upstream: Switch hpdelim interface to accept only ":" as delimiter.

upstream: Switch hpdelim interface to accept only ":" as delimiter.

Historicallly, hpdelim accepted ":" or "/" as a port delimiter between
hosts (or addresses) and ports.  These days most of the uses for "/"
are no longer accepted, so there are several places where it checks the
delimiter to disallow it.  Make hpdelim accept only ":" and use hpdelim2
in the other cases.  ok djm@

OpenBSD-Commit-ID: 7e6420bd1be87590b6840973f5ad5305804e3102