progs/glsl: compile with scons and glew

Get most of these working with scons.
diff --git a/progs/SConscript b/progs/SConscript
index 71ebe5e..620dd30 100644
--- a/progs/SConscript
+++ b/progs/SConscript
@@ -1,6 +1,7 @@
 SConscript([
     'util/SConscript',
     'demos/SConscript',
+    'glsl/SConscript',
     'redbook/SConscript',
     'samples/SConscript',
     'tests/SConscript',