progs/trivial: Add quad-tex-sub

   Tests glTexSubImage
diff --git a/progs/trivial/SConscript b/progs/trivial/SConscript
index 9444cdb..6a9ffaf 100644
--- a/progs/trivial/SConscript
+++ b/progs/trivial/SConscript
@@ -66,6 +66,7 @@
 	'quad-tex-3d',
 	'quad-tex-alpha',
 	'quad-tex-pbo',
+	'quad-tex-sub',
 	'quad-unfilled-clip',
 	'quad-unfilled-stipple',
 	'quad-unfilled',