patch 8.0.0367: types in include files may be inconsistent

Problem:    If configure defines _LARGE_FILES some include files are included
            before it is defined.
Solution:   Include vim.h first. (Sam Thursfield, closes #1508)

src/gui_xmdlg.c

@@ -16,6 +16,8 @@
  * when using a dynamic scrollbar policy.
  */
 
+#include "vim.h"
+
 #include <Xm/Form.h>
 #include <Xm/PushBG.h>
 #include <Xm/Text.h>
@@ -36,8 +38,6 @@
 #include <X11/StringDefs.h>
 #include <X11/Intrinsic.h>
 
-#include "vim.h"
-
 extern Widget vimShell;
 
 #ifdef FEAT_MENU