Also fix #3499.  The issue was solved by #3462.

Instead of shifting mruby VM stack, we always use CALL_MAXARGS.

There are 3 levels of C++ exception handling:
* default - no C++ exception (use setjmp/longjmp)
* enable_cxx_exception (use C++ exceptions with C ABI)
* enable_cxx_abi (use C++ ABI including exceptions)

`mrb_funcall()` recursion can cause stack overflow easily,
so recursion depth is now limited to MRB_FUNCALL_DEPTH_MAX,
which default value is 512.

But #3421 still cause stack overflow error due to infinite recursion.
To prevent overflow, we need to add different stack depth check.

This issue was reported by https://hackerone.com/d4nny

The issue was reported by https://hackerone.com/titanous

There's incompatibility left for mruby.

When you return from `ensure` clause, mruby simply ignores the return
value.  CRuby returns from the method squashing the exception raised.

```
def f
  no_such_method() # NoMethodError
ensure
  return 22
end

p f() # CRuby prints `22`
```

OP_RETURN accesses ci[1]->stackent that might be broken; fix #3442