help: unify handling of DEPRECATED/EXPERIMENTAL keywords This fixes listexts() to exclude translated "(DEPRECATED)" marker correctly. On the other hand, help_() doesn't need translated keywords, but I don't think it's worth to separate untranslated keywords just for it.

help: include parens in DEPRECATED/EXPERIMENTAL keywords In some languages that have no caps, "DEPRECATED" and "deprecated" can be translated to the same byte sequence. So it is too wild to exclude messages by _("DEPRECATED").