xgettext: Simplify calling convention of remember_a_message.
* gettext-tools/src/xg-message.h (remember_a_message,
remember_a_message_plural): Add is_utf8, comment_is_utf8 arguments.
* gettext-tools/src/xg-message.c (remember_a_message,
remember_a_message_plural): Likewise.
* gettext-tools/src/xg-arglist-parser.c (arglist_parser_done): Update callers.
* gettext-tools/src/x-awk.c (extract_parenthesized): Likewise.
* gettext-tools/src/x-c.c (extract_parenthesized): Likewise.
* gettext-tools/src/x-csharp.c (extract_parenthesized): Likewise.
* gettext-tools/src/x-desktop.c (extract_desktop_handle_pair): Likewise.
* gettext-tools/src/x-elisp.c (read_object): Likewise.
* gettext-tools/src/x-java.c (extract_parenthesized): Likewise.
* gettext-tools/src/x-javascript.c (extract_balanced): Likewise.
* gettext-tools/src/x-librep.c (read_object): Likewise.
* gettext-tools/src/x-lisp.c (read_object): Likewise.
* gettext-tools/src/x-lua.c (extract_balanced): Likewise.
* gettext-tools/src/x-perl.c (extract_variable, interpolate_keywords,
extract_balanced): Likewise.
* gettext-tools/src/x-php.c (extract_balanced): Likewise.
* gettext-tools/src/x-python.c (extract_balanced): Likewise.
* gettext-tools/src/x-rst.c (extract_rst, extract_rsj): Likewise.
* gettext-tools/src/x-scheme.c (read_object): Likewise.
* gettext-tools/src/x-sh.c (read_word, read_command): Likewise.
* gettext-tools/src/x-smalltalk.c (extract_smalltalk): Likewise.
* gettext-tools/src/x-tcl.c (read_command): Likewise.
* gettext-tools/src/x-vala.c (extract_balanced): Likewise.
* gettext-tools/src/x-ycp.c (extract_parenthesized): Likewise.
* gettext-tools/src/xgettext.c (xgettext_its_extract_callback): Likewise.
