6897844: Fix broken build on newer versions of X11 (libXext >= 1.1.0)

Summary: Recent changes to X11's header structure break the build
Reviewed-by: prr, flar

src/solaris/native/sun/awt/awt_GraphicsEnv.h

@@ -42,6 +42,10 @@
 #include <sys/ipc.h>
 #include <sys/shm.h>
 #include <X11/extensions/XShm.h>
+#ifndef X_ShmAttach
+#include <X11/Xmd.h>
+#include <X11/extensions/shmproto.h>
+#endif
 
 extern int XShmQueryExtension();