Some common headers ported over to LuaJIT FFI

For some of these I use a $LUAJIT_LIBPATH environment variable to specify the base of the directory structure where .so files are located.
From there sometimes I follow Malkia's structure of /$ffi.os/$ffi.arch/ to further distinguish .so files.

I must give props to https://github.com/malkia/ufo from which some of these may have come, or at least the notion of doing such a thing came from.