Fix broken dependency of AVarGraph.h on a declaration of AVarBoundsInfo

as an incomplete type, exposed by the previous commit.

I chose to do so by including ABounds.h since that's what
AVarBoundsInfo.h does, though simply declaring AVarBoundsInfo might have
worked.

Author: mattmccutchen-cci

clang/include/clang/3C/AVarGraph.h

@@ -13,6 +13,7 @@
 #ifndef _AVARGRAPH_H
 #define _AVARGRAPH_H
 
+#include "ABounds.h"
 #include "ConstraintsGraph.h"
 
 // Graph that keeps tracks of direct assignments between various variables.