include: move BUG_*() macros to separate header

Yet another step of uncluttering includes: move out the BUG_* macros
into a separate header, which then is included as-needed.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>

dix/inpututils.c

@@ -27,6 +27,7 @@
 #include "dix-config.h"
 #endif
 
+#include "bug.h"
 #include "exevents.h"
 #include "exglobals.h"
 #include "misc.h"