Code sprint: TCC::Callable is in, FFI bindings are out.

This includes a major code sprint to implement my own arbitrary
function caller. I think I have it mostly figured out. Unfortunately,
I cannot get the library to compile on my Mac, so I can't be sure
without running it on a different machine... which means comitting
and pushing my latest.
Tweaked Build.PL for better tcc detection diagnostics
Updated tcc_relocate to new calling convention
Merge work