tgsi/scan: update for POSITION and FACE sytem values
tgsi/scan: update for POSITION and FACE sytem values

Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com
Reviewed-by: Brian Paul <3cb4e1df5ec4da2c7c4af7c52cec8cf340a55a10@vmware.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler