its: Simplify.
* gettext-tools/src/its.h: Don't include xg-arglist-context.h.
(its_rule_list_extract): Remove flag_table parameter.
* gettext-tools/src/its.c (its_rule_list_extract_text, its_rule_list_extract):
Remove flag_table parameter.
* gettext-tools/src/xgettext.c (extract_from_xml_file): Update.
