:cquit : take an error code argument #7336

closes #2699

ex_cmds.lua: use flags consistent with similar commands such as `cnext`.

upstream discussion:
"[patch] :qcuit can take exit code"
https://groups.google.com/d/msg/vim_dev/_PjyNbUKyRc/oPgr5_ZXc6AJ

src/nvim/ex_docmd.c

@@ -9,6 +9,7 @@
 #include <string.h>
 #include <stdbool.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <inttypes.h>
 
 #include "nvim/vim.h"
@@ -5995,7 +5996,7 @@ static void ex_quit(exarg_T *eap)
  */
 static void ex_cquit(exarg_T *eap)
 {
-  getout(1);
+  getout(eap->addr_count > 0 ? (int)eap->line2 : EXIT_FAILURE);
 }
 
 /*