Use angle brackets (<>) rather than quotes ("") for the include
directives in our .h files. This should avoid some potentially nasty
surprises for Winelib apps.

diff --git a/include/initguid.h b/include/initguid.h
index 976dd78..b69c925 100644
--- a/include/initguid.h
+++ b/include/initguid.h
@@ -23,4 +23,4 @@
  */
 
 #define INITGUID
-#include "guiddef.h"
+#include <guiddef.h>