Pi3 build: Added support for four controllers

This version now supports four controllers when the machine type is set to 400/800.

Be sure to remember to set the two additional controllers to "Atari Joystick" under Controls (they default to RetroPad).

Installation:

cd ~

sudo wget https://github.com/raphkoster/libretro-atari800/releases/download/v.3.1.0.2-alpha/atari800_libretro.so

sudo cp /opt/retropie/libretrocores/lr-atari800/atari800_libretro.so /opt/retropie/libretrocores/lr-atari800/atari800_libretro.so-backup

sudo chmod a+x atari800_libretro.so

sudo mv atari800_libretro.so /opt/retropie/libretrocores/lr-atari800/atari800_libretro.so

Raspberry Pi 3 build to fix SHIFT/CTRL

This fixes the missing SHIFT and CTRL behavior when typing in Atari 800 emulation. You can now type shifted characters, the graphical control characters, and lowercase characters.

Known issue: the virtual keyboard does not seem to function.

This build is specifically for Raspberry Pi, compiled on a 3 running Stretch.

To install:

cd ~

sudo wget https://github.com/raphkoster/libretro-atari800/releases/download/v.3.1.0.1-alpha/atari800_libretro.so

sudo cp /opt/retropie/libretrocores/lr-atari800/atari800_libretro.so /opt/retropie/libretrocores/lr-atari800/atari800_libretro.so-backup

sudo chmod a+x atari800_libretro.so

sudo mv atari800_libretro.so /opt/retropie/libretrocores/lr-atari800/atari800_libretro.so