mesa: trim down #includes in api_loopback.h
mesa: trim down #includes in api_loopback.h

Acked-by: Matt Turner <789b315743a28dd066a4ba1459c35951c291d8a6@gmail.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler