vim-patch:7.4.1777

Problem:    Newly added features can escape the sandbox.
Solution:   Add checks for restricted and secure. (Yasuhiro Matsumoto)
3849992b16

timer_start is missing check_secure.

The timer callback can, for example, call a function defined from outside the sandbox that does
stuff that would be disallowed from inside the sandbox. This is usually not allowed.

Cherry-pick eval.txt change from:
68e6560b84

Required for v8.1.2013.

src/nvim/eval/funcs.c

@@ -11551,6 +11551,9 @@ static void f_timer_start(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   dict_T *dict;
 
   rettv->vval.v_number = -1;
+  if (check_secure()) {
+    return;
+  }
 
   if (argvars[2].v_type != VAR_UNKNOWN) {
     if (argvars[2].v_type != VAR_DICT