Add rcamera and fix a raygui linker issue

This adds a binding for rcamera.h, which I didn't realize was not included in raylib.h

It's automatically imported by importing raylib, so you don't need to do anything to start using it, if you are already using raylib.

This also fixes a bug that someone discovered when using the raygui port on Windows, as raylib has added some of the raygui functions to its core library.