Stop c32rtomb and mbrtoc32 aliasing wcrtomb and mbrtowc (bug 23793)

[Florian Weimer]

* Joseph Myers:

> 2018-10-19  Joseph Myers  <joseph@codesourcery.com>
>
> 	[BZ #23793]
> 	* wcsmbs/c32rtomb.c: New file.
> 	* wcsmbs/mbrtoc32.c: Likewise.
> 	* wcsmbs/tst-c32-state.c: Likewise.
> 	* wcsmbs/mbrtowc.c (mbrtoc32): Do not define as alias.
> 	* wcsmbs/wcrtomb.c (c32rtomb): Likewise.
> 	* wcsmbs/Makefile (routines): Add mbrtoc32 and c32rtomb.
> 	(tests): Add tst-c32-state.
> 	[$(run-built-tests) = yes] ($(objpfx)tst-c32-state.out): Depend on
> 	$(gen-locales).

Patch and test look good to me.  Thanks.

Florian