progs/tests: compile with SCons and glew

Also get mingw cross-compilation of these tests working
diff --git a/progs/tests/bufferobj.c b/progs/tests/bufferobj.c
index 9edb86e..1d97b06 100644
--- a/progs/tests/bufferobj.c
+++ b/progs/tests/bufferobj.c
@@ -6,11 +6,11 @@
  */
 
 
-#define GL_GLEXT_PROTOTYPES
 #include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <math.h>
+#include <GL/glew.h>
 #include <GL/glut.h>
 
 #define NUM_OBJECTS 10
@@ -428,6 +428,7 @@
    glutInitWindowSize( 600, 300 );
    glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
    Win = glutCreateWindow(argv[0]);
+   glewInit();
    glutReshapeFunc( Reshape );
    glutKeyboardFunc( Key );
    glutSpecialFunc( SpecialKey );