[Patch] Add C11 uchar/wchar related __STDC_* definitions

[Ed Schouten]

Hi,

It seems that even though Clang uses UTF-16 and UTF-32 for char*_t
string literals exclusively, we don't define __STDC_UTF_16__ and
__STDC_UTF_32__ yet.

Also, on FreeBSD, we have to define __STDC_MB_MIGHT_NEQ_WC__, as
wchar_t uses the code points of the current locale; not ISO 10646.
This means that we should not define __STDC_MB_MIGHT_NEQ_WC__ and
__STDC_ISO_10646__, as one could in theory use a locale that is not a
superset of ASCII (e.g. CP437).

Patch:

http://80386.nl/pub/clang-c11-uchar.txt

--
Ed Schouten <ed at 80386.nl>