patch 8.2.2247: VMS: various smaller problems

Problem:    VMS: various smaller problems.
Solution:   Fix VMS building and other problems. (Zoltan Arpadffy)
diff --git a/src/os_unix.h b/src/os_unix.h
index 9b7337a..46f4bba 100644
--- a/src/os_unix.h
+++ b/src/os_unix.h
@@ -199,10 +199,11 @@
 # include <libdef.h>
 # include <libdtdef.h>
 
-# ifdef FEAT_GUI_GTK
-#  include "gui_gtk_vms.h"
+# if defined(FEAT_GUI_MOTIF)
+#  define XFree XFREE
+#  define XmRepTypeInstallTearOffModelCon XMREPTYPEINSTALLTEAROFFMODELCON
 # endif
-#endif
+#endif // VMS
 
 #ifdef HAVE_FLOCK
 # include <sys/file.h>