CMake: Use internal libs.
Adds an option to use the libraries included with the source code. Most of the work was done by @MonsterIestyn. This is just fixes up some things and adds a 64-bit libgme.
Adds an option to use the libraries included with the source code. Most of the work was done by @MonsterIestyn. This is just fixes up some things and adds a 64-bit libgme.