patch 8.1.0766: various problems when using Vim on VMS

Problem:    Various problems when using Vim on VMS.
Solution:   Various fixes. Define long_long_T. (Zoltan Arpadffy)
diff --git a/src/gui_x11.c b/src/gui_x11.c
index 9d8ea7e..1c55805 100644
--- a/src/gui_x11.c
+++ b/src/gui_x11.c
@@ -30,7 +30,11 @@
 # include <Xm/XpmP.h>
 #else
 # ifdef HAVE_X11_XPM_H
-#  include <X11/xpm.h>
+#  ifdef VMS
+#   include <xpm.h>
+#  else
+#   include <X11/xpm.h>
+#  endif
 # endif
 #endif