MFC r263998:

Rename __wchar_t so it no longer conflicts with __wchar_t from clang 3.4
-fms-extensions.
MFC r263986:

- In the libiconv module for ISO 2022 restore the original order of the
  fields of a private struct such that variables of this type are
  initialised correctly.  Fixes conversion from ISO 2022.
  Also do this in the BIG5 module to prevent similar errors in the future.
- In the libiconv module for EUC-TW replace 2^cs with 1<<cs.  Fixes
  conversion from EUC-TW.
- Synchronise iconv code with NetBSD.  In most cases this only updates
  the RCS id because the changes are already there or are NetBSD specific.
  + libc/iconv/citrus_csmapper.c: Add a comment.
  + libc/iconv/citrus_db_factory.c: Remove put16().
  + libc/iconv/citrus_iconv.c: Return EINVAL on error.
  + libc/iconv/citrus_mapper.c: Return EINVAL on error.
  + libc/iconv/citrus_memstream.c: Fix type of a variable.
  + libc/iconv/citrus_prop.h: Sync definition of _CITRUS_PROP_HINT_END.
  + libc/iconv/citrus_stdenc.c: Return EINVAL on error.
  + libiconv_modules/mapper_std/citrus_mapper_std.c: Plug memory leak.

Obtained from:	NetBSD