Add named sequences to Unicode wildcard name capabilites

Add named sequences to Unicode wildcard name capabilites

Prior to this commit, specifying a named sequence would result in a
mostly unhelpful fatal error message.  This makes their use legal.

This is also the beginning of allowing Unicode string properties, which
are a new thing in the (still draft) Unicode requirements for regular
expression parsing, UTS 18.  Full compliance will have to come later.