reg_namedseq: Restructure so doesn't duplicate code

reg_namedseq: Restructure so doesn't duplicate code

This routine now calls reg() recursively after converting the parse
to something the rest of the code understands.  This eliminates
duplicated code, and allows for uniform treatment of code points, as
things were getting out of sync.  It also eliminates the restrction on
how many characters a named sequence can expand to.

toke now converts its input (which is in Unicode terms) to native on
EBCDIC platforms, so the rest of the code can can continue to ignore
that.

The restriction on the length of the number of characters a named
sequence is hereby removed, because reg() handles that.