Ensures GYP always invokes LuaJIT makefile.
Performs stringification of keys in assignment in JIT.
Adds testcase for NOT on negative numbers. Fixes #605.
Restores FFI support on Linux.
Makes luajit-build work on Darwin/GCC. Fixes Buffer incompat.
Merge #607 r=@kevinmehall: Minor fixes for colonyinterpreter build.