MFC r295147:
Make dynamic link of libiconv from ports work again.
The symbols of libiconv from ports were changed to
have prefixed.
Since we have iconv in our libc these days, we don't
need it on 10.X and later. However, 9.X still need
this.

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Check error of dlfunc(3).

MFC after: 3 days

Enable NLS catalog of csh(1).
The tcsh 6.14 uses libiconv to convert catalogs to appropriate charset
dynamically. However, we don't have libiconv in our tree. So, I made
some hack to load libiconv dynamically. If libiconv is available, you
can use catalogs for more locales than the locales which catalog is
actually installed.
To use this feature, you need to symlink catalogs to appropriate
locales. You can do this by installing ports/shells/tcsh_nls.

Reviewed by: arch (no objection)
MFC after: 1 week