mark Quit() & QuitAction() as noreturn

Clears gcc warnings:

xfontsel.c: In function ‘QuitAction’:
xfontsel.c:1477:1: warning: function might be candidate for
 attribute ‘noreturn’ [-Wsuggest-attribute=noreturn]
 QuitAction(Widget w, XEvent *event, String *params, Cardinal *num_params)
 ^~~~~~~~~~

xfontsel.c: In function ‘Quit’:
xfontsel.c:1392:6: warning: function might be candidate for
 attribute ‘noreturn’ [-Wsuggest-attribute=noreturn]
 void Quit(Widget w, XtPointer closure, XtPointer callData)
      ^~~~
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>

configure.ac

@@ -37,7 +37,7 @@ m4_ifndef([XORG_MACROS_VERSION],
 XORG_MACROS_VERSION(1.8)
 XORG_DEFAULT_OPTIONS
 
-PKG_CHECK_MODULES(XFONTSEL, xaw7 xmu xt x11)
+PKG_CHECK_MODULES(XFONTSEL, xaw7 xmu xt x11 xproto >= 7.0.17)
 
 PKG_CHECK_MODULES(APPDEFS, xt)
 xt_appdefaultdir=`$PKG_CONFIG --variable=appdefaultdir xt`

xfontsel.c

@@ -67,7 +67,7 @@ Modified: Mark Leisher <mleisher@crl.nmsu.edu> to deal with UCS sample text.
 void GetFontNames(XtPointer closure);
 Boolean Matches(String pattern, String fontName, Boolean fields[], int *maxfields);
 Boolean DoWorkPiece(XtPointer closure);
-void Quit(Widget w, XtPointer closure, XtPointer callData);
+void Quit(Widget w, XtPointer closure, XtPointer callData) _X_NORETURN;
 void OwnSelection(Widget w, XtPointer closure, XtPointer callData);
 void SelectField(Widget w, XtPointer closure, XtPointer callData);
 void ParseFontNames(XtPointer closure);
@@ -79,7 +79,8 @@ void AnyValue(Widget w, XtPointer closure, XtPointer callData);
 void EnableOtherValues(Widget w, XtPointer closure, XtPointer callData);
 void EnableMenu(XtPointer closure);
 void SetCurrentFont(XtPointer closure);
-void QuitAction(Widget w, XEvent *event, String *params, Cardinal *num_params);
+void QuitAction(Widget w, XEvent *event, String *params, Cardinal *num_params)
+    _X_NORETURN;
 
 static XtActionsRec xfontsel_actions[] = {
     {"Quit",	    QuitAction}