progs: Port most of the demos to glew.

A couple of test weren't ported due to glew breakage -- it undefines
GLAPIENTRY.
diff --git a/progs/demos/streaming_rect.c b/progs/demos/streaming_rect.c
index 4c1d853..4d4656e 100644
--- a/progs/demos/streaming_rect.c
+++ b/progs/demos/streaming_rect.c
@@ -6,12 +6,11 @@
  *
  */
 
-#define GL_GLEXT_PROTOTYPES
-
 #include <math.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <GL/glew.h>
 #include <GL/glut.h>
 
 #include "readtex.h"
@@ -303,6 +302,7 @@
    glutInitWindowPosition( 0, 0 );
    glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
    glutCreateWindow(argv[0] );
+   glewInit();
 
    Init( argc, argv );