[Issue 32] Xproto type conflict

Please review. 

This changes Xlibint.d so that the types `GContext, KeySym, Font, VisualID, Window` come from X.d and not Xproto.d: 

I believe this is correct and matches how the types will propagate through the C header files to Xlibint.h.

My understanding is that Xlibint.h gets these types from X.h via `#include <Xlib.h>`. The types in Xproto.h are all #defines and #undef at the end of Xproto.h so they do not escape the Xproto.h header file.

However, I do get nervous when I read this from Xlibint.h...
```C
/*
[snip]
 *
 *	Warning, there be dragons here....
 */
```