Adds benchmarks for nallocx, calloc, alloc, alloc_excess, ralloc, ralloc_excess

[gnzlbg]

No description provided.

[gnzlbg]

@alexcrichton I am adding these benchmarks to jemallocator even though they only use jemalloc-sys, I hope that is ok.

[SimonSapin]

Its a lot of boilerplate that I don't seem to be able to avoid because I cannot concatenate identifiers to form new identifiers in macros.

Rather than generating functions whose names are concatenated identifiers, I’ve had some success making macros generate functions in modules. So instead of ${foo}_${bar} you end up with $foo::$bar for example.

[gnzlbg]

@SimonSapin the problem I ran into was that I had the size and align as part of the test name. I would have to move them to be part of the module's name, but I don't think that is possible.

[alexcrichton]

Can this be left out to a future PR?

The submodule update here I don't think shoudl be run with run which asserts success, it should just be opportunistic and should provide a better failure message unrelated to git if the git step ends up failing.

[gnzlbg]

@alexcrichton the submodule update is a mistake in this PR, i have reverted it.

I have it in a separate PR, but git add -u pulled into all my other PRs making i686-apple builds fail... Sorry about that.