Added plat_load_system_gl implementation for posix platforms.
Added plat_load_system_gl implementation for posix platforms.

bclemetsonblizzard/vogl,kingtaurus/vogl,kingtaurus/vogl,ValveSoftware/vogl,bclemetsonblizzard/vogl,ValveSoftware/vogl,ValveSoftware/vogl,bclemetsonblizzard/vogl,ValveSoftware/vogl,kingtaurus/vogl,bclemetsonblizzard/vogl,kingtaurus/vogl,bclemetsonblizzard/vogl