support (ignore) universal ctags extended metadata in tagaddress

support (ignore) universal ctags extended metadata in tagaddress

universal ctags "abuses" the tagaddress, which can be an arbitrary
vi command even if mg assumes it's just a search pattern, to store
metadata after a "vi comment".

While it could be worthwile to support the uctags annotations this
just ignores them so the search patterns work again.

The diff is from Joachim Wiberg "troglobit" mg.

ok tb@