patch 9.0.1538: :wqall does not trigger ExitPre

Problem:    :wqall does not trigger ExitPre. (Bart Libert)
Solution:   Move preparations for :qall to a common function. (closes #12374)
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index a0a7183..430ca2c 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -5957,10 +5957,11 @@
 }
 
 /*
- * ":qall": try to quit all windows
+ * Do preparations for "qall" and "wqall".
+ * Returns FAIL when quitting should be aborted.
  */
-    static void
-ex_quit_all(exarg_T *eap)
+    int
+before_quit_all(exarg_T *eap)
 {
     if (cmdwin_type != 0)
     {
@@ -5968,19 +5969,30 @@
 	    cmdwin_result = K_XF1;	// ex_window() takes care of this
 	else
 	    cmdwin_result = K_XF2;
-	return;
+	return FAIL;
     }
 
     // Don't quit while editing the command line.
     if (text_locked())
     {
 	text_locked_msg();
-	return;
+	return FAIL;
     }
 
     if (before_quit_autocmds(curwin, TRUE, eap->forceit))
-	return;
+	return FAIL;
 
+    return OK;
+}
+
+/*
+ * ":qall": try to quit all windows
+ */
+    static void
+ex_quit_all(exarg_T *eap)
+{
+    if (before_quit_all(eap) == FAIL)
+	return;
     exiting = TRUE;
     if (eap->forceit || !check_changed_any(FALSE, FALSE))
 	getout(0);