wctype: out of bound access in POSIX locale.

The POSIX locale has gLocaleRoster = NULL and relies on the non-wide
version of the implementation. However it doesn't check that the
characters are actually in range which leads to out of bound access and
crashes in __isctype.

Fixes #11322.
test_app_server: use libstackandtile.

We build a static lib for it, so we may as well use it.