Fix warnings in compilation on Windows

[CodingALS]

No description provided.

[CodingALS]

@Oen44

[Oen44]

Well... I kind of have few comments here.

1. Stop using C-style casting, even when its already used in the sources. If you are editing them or adding new one then use C++ casting from standard lib.
2. This luaL_newlib macro check and definition can be shortened

#ifndef luaL_newlib
#define luaL_newlib(x, y) luaL_register(x, LUA_BIT32LIBNAME, y)
#endif

[CodingALS]

Yeah, I just wanted to keep the default used in the source, since the preprocessor defined in the LIBs is different from the one used in the "standard source".