build: Fix Woe32 cross build
* msgfmt.c (add_languages): New function split from get_languages.
(get_languages): Use add_languages instead of manually parsing
LINGUAS envvar with strtok_r possibly provided by libgettextlib.
* x-c.h (literalstring_c): Remove unnecessary DLL_VARIABLE.
* xgettext.c (arglist_parser_alloc): Use LET_NONE instead of 0.
(arglist_parser_remember): Likewise.
* xgettext.h (enum literalstring_escape_type): New enum value
LET_NONE.
* woe32dll/gettextsrc-exports.c: Don't export line_comment and
po_lex_iconv if undefined.
