progs/tests: compile with SCons and glew

Also get mingw cross-compilation of these tests working
diff --git a/progs/tests/multitexarray.c b/progs/tests/multitexarray.c
index b4fab00..518fee2 100644
--- a/progs/tests/multitexarray.c
+++ b/progs/tests/multitexarray.c
@@ -16,6 +16,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include "GL/glew.h"
 #include "GL/glut.h"
 
 static GLuint Window = 0;
@@ -221,6 +222,7 @@
    glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
 
    Window = glutCreateWindow("Texture Objects");
+   glewInit();
    if (!Window) {
       exit(1);
    }