patch 9.0.2153: no support to build on OpenVMS

Problem:  no support to build on OpenVMS
Solution: Add OpenVMS X86_64 platform port

closes: #13623

Co-authored-by: errael <errael@raelity.com>
Co-authored-by: K.Takata <kentkt@csc.jp>
Signed-off-by: Zoltan Arpadffy <zoltan.arpadffy@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/gui.h b/src/gui.h
index 7bcbfa3..0a1d274 100644
--- a/src/gui.h
+++ b/src/gui.h
@@ -12,15 +12,9 @@
 #endif
 
 #ifdef FEAT_GUI_GTK
-# ifdef VMS // undef MIN and MAX because Intrinsic.h redefines them anyway
-#  ifdef MAX
-#   undef MAX
-#  endif
-#  ifdef MIN
-#   undef MIN
-#  endif
+# ifdef VMS
 #  include "gui_gtk_vms.h"
-# endif // VMS
+# endif
 # include <X11/Intrinsic.h>
 # pragma GCC diagnostic push
 # pragma GCC diagnostic ignored "-Wstrict-prototypes"