include readtex.h instead of readtex.c
diff --git a/progs/demos/winpos.c b/progs/demos/winpos.c
index 6250419..2ee1df6 100644
--- a/progs/demos/winpos.c
+++ b/progs/demos/winpos.c
@@ -14,7 +14,7 @@
 #define GL_GLEXT_PROTOTYPES
 #include "GL/glut.h"
 
-#include "readtex.c"  /* a hack, I know */
+#include "readtex.h"
 
 #define IMAGE_FILE "../images/girl.rgb"