* iconv/gconv_open.c (__gconv_open): Empty codeset name now means using
the current locale's codeset.
* iconv/iconv_open.c (iconv_open): Don't strip out everything for
empty input string.
* iconv/iconv_prog.c: Pass empty strings as default value for to-
and from-charset. Don't determine locale's charset here.
if libio is used [PR libc/2575].