C++ screening

[zingale]

This ports screen5 to C++. It also makes the number of screenings known at build time (as NSCREEN in C++) -- this greatly simplifies the initialization logic.

[zingale]

diffs between F90 and C++ (using the test_screening{_C} unit tests

            variable name            absolute error            relative error
                                        (||A - B||)         (||A - B||/||A||)
 ----------------------------------------------------------------------------
 level = 0
 density                                          0                         0
 temperature                                      0                         0
 X_hydrogen-1                                     0                         0
 X_helium-3                                       0                         0
 X_helium-4                                       0                         0
 X_carbon-12                                      0                         0
 X_nitrogen-14                                    0                         0
 X_oxygen-16                                      0                         0
 X_neon-20                                        0                         0
 X_magnesium-24                                   0                         0
 X_silicon-28                                     0                         0
 X_sulfur-32                                      0                         0
 X_argon-36                                       0                         0
 X_calcium-40                                     0                         0
 X_titanium-44                                    0                         0
 X_chromium-48                                    0                         0
 X_chromium-56                                    0                         0
 X_iron-52                                        0                         0
 X_iron-54                                        0                         0
 X_iron-56                                        0                         0
 X_nickel-56                                      0                         0
 X_neutron                                        0                         0
 X_proton                                         0                         0
 scn_he4_he4                                3342336           2.533737209e-19
 scn_he4_be8                        1.918461384e+22           2.031274287e-22
 scn_c12_he4                        4.880759047e+35           1.983157552e-25
 scn_c12_c12                                  1e+98           1.346427863e-17
 scn_c12_o16                        1.064175617e+82           5.478589148e-49
 scn_o16_o16                                  1e+98           3.943668288e-23
 scn_o16_he4                        1.375866776e+48            6.66642117e-28
 scn_ne20_he4                       2.589304466e+59           1.697347984e-30
 scn_mg24_he4                        1.05143792e+70           5.942028057e-33
 scn_al27_p                         2.723468086e+29           2.844301281e-17
 scn_si28_he4                       7.622325019e+41           1.633170668e-73
 scn_p31_p                          1.152040865e+34           1.583077536e-17
 scn_s32_he4                        5.450662671e+89            1.50624283e-37
 scn_cl35_p                         1.254791228e+39           3.620525265e-17
 scn_ar36_he4                                 1e+98             2.0871336e-31
 scn_k39_p                          2.568967367e+25           2.316948484e-35
 scn_ca40_he4                        1.81447472e+58           9.341279159e-73
 scn_sc43_p                         1.548563747e+47           6.162290306e-18
 scn_ti44_he4                                 1e+98           4.348584378e-14
 scn_v47_p                          1.555037742e+51           3.696057417e-18
 scn_cr48_he4                       1.979871083e+68           1.019277275e-62
 scn_mn51_p                          1.20205119e+55           2.233643649e-18
 scn_fe52_he4                       1.432290921e+89           7.373720437e-42
 scn_co55_p                         1.479042096e+59           2.735798982e-18
 scn_fe54_p                          9.74667164e+56           1.721844496e-18
 scn_fe54_he4                       2.661313391e+73           1.370097419e-57
 scn_fe56_p                         9.869271283e+56           1.679979674e-18
 scn_d_p                            3.259629011e-09           3.615137393e-16
 scn_p_p                            1.862645149e-09           9.022327079e-16
 scn_he3_he3                                1572864           2.248652584e-17
 scn_he3_he4                                1572864           2.101221055e-18
 scn_c12_p                                    11.25           3.865470379e-26
 scn_n14_p                          7.586630232e+13             2.0455301e-16
 scn_o16_p                                    75776           2.185560651e-28
 scn_n14_he4                        1.557132111e+42           1.536313276e-26
 scn_he4_he4_dt                                 132           5.242022723e-19
 scn_he4_be8_dt                     1.279022294e+18           4.051469139e-22
 scn_c12_he4_dt                     4.373394571e+31           3.867230519e-25
 scn_c12_c12_dt                               1e+98           8.161881244e-15
 scn_c12_o16_dt                     1.303703025e+92           4.422433475e-34
 scn_o16_o16_dt                               1e+98           5.921923526e-15
 scn_o16_he4_dt                     1.561052164e+44           1.318749469e-27
 scn_ne20_he4_dt                    3.428958773e+55           3.307287119e-30
 scn_mg24_he4_dt                    1.619176484e+66           1.173687005e-32
 scn_al27_p_dt                      1.964504457e+25           5.847053038e-17
 scn_si28_he4_dt                    4.718759385e+37           1.155806537e-73
 scn_p31_p_dt                       9.309309095e+29           3.294821295e-17
 scn_s32_he4_dt                     1.049041202e+86           3.001489371e-37
 scn_cl35_p_dt                      1.122834196e+35           7.639474896e-17
 scn_ar36_he4_dt                    8.468854849e+95           1.937948196e-14
 scn_k39_p_dt                       5.316911983e+36           1.045649903e-19
 scn_ca40_he4_dt                              1e+98           4.617122893e-17
 scn_sc43_p_dt                       1.61157729e+43           1.303545647e-17
 scn_ti44_he4_dt                              1e+98           5.687235212e-14
 scn_v47_p_dt                       1.691288516e+47           7.666603024e-18
 scn_cr48_he4_dt                    1.157920892e+77           1.854723745e-36
 scn_mn51_p_dt                      1.397195565e+51           4.671060595e-18
 scn_fe52_he4_dt                    7.831383972e+84           1.463403363e-35
 scn_co55_p_dt                      1.815049406e+55           5.724360786e-18
 scn_fe54_p_dt                      1.167330588e+53           3.609559659e-18
 scn_fe54_he4_dt                    1.214168058e+83           2.102788275e-37
 scn_fe56_p_dt                      1.182296365e+53            3.52187883e-18
 scn_d_p_dt                         3.552713679e-14           7.339598803e-16
 scn_p_p_dt                         1.598721155e-14           1.470810806e-15
 scn_he3_he3_dt                                56.5           4.651780568e-17
 scn_he3_he4_dt                                  59           4.343964563e-18
 scn_c12_p_dt                                 98304           1.674750123e-17
 scn_n14_p_dt                            3456106496           4.134422272e-16
 scn_o16_p_dt                                     4           4.650497836e-28
 scn_n14_he4_dt                     1.608365875e+38           3.065344013e-26

[dwillcox]

All looks good, thanks!