Consistently use platform-specific function to detect window system.

* lisp.h (check_window_system): New prototype.  This function is
going to replace check_x, check_w32 and check_ns.
(have_menus_p): Mention msdos.c in comment.
* fontset.c (check_window_system_func): Remove.  Adjust all users.
* fontset.h (check_window_system_func): Remove prototype.
* nsterm.h (check_ns):
* xterm.h (check_x):
* w32term.h (check_w32): Likewise.
* menu.c (Fx_popup_menu): Use check_window_system.
* msdos.c (check_window_system): Define for MS-DOS.
* nsfns.m (check_window_system): Define for NS.  Adjust all users.
* w32fns.c (check_window_system): Likewise for MS-Windows.
* xfns.c (check_window_system): Likewise for X.
* font.c, frame.c, nsmenu.m, nsselect.m, nsterm.m, w32menu.c:
* xfaces.c, xmenu.c: Use check_window_system where appropriate.

1 files changed, 2 insertions, 6 deletions

diff --git a/src/fontset.c b/src/fontset.c
index 3578bc9403d..7aec26bbb5b 100644
--- a/src/fontset.c
+++ b/src/fontset.c
@@ -179,10 +179,6 @@ static int next_fontset_id;
    font for each character.  */
 static Lisp_Object Vdefault_fontset;
 
-/* Check if any window system is used now.  */
-void (*check_window_system_func) (void);
-
-
 /* Prototype declarations for static functions.  */
 static Lisp_Object make_fontset (Lisp_Object, Lisp_Object, Lisp_Object);
 
@@ -1213,7 +1209,7 @@ If REGEXPP is non-nil, PATTERN is a regular expression.  */)
   Lisp_Object fontset;
   int id;
 
-  (*check_window_system_func) ();
+  check_window_system ();
 
   CHECK_STRING (pattern);
 
@@ -1919,7 +1915,7 @@ format is the same as above.  */)
   Lisp_Object val, elt;
   int c, i, j, k;
 
-  (*check_window_system_func) ();
+  check_window_system ();
 
   fontset = check_fontset_name (fontset, &frame);