Amend the way we handle ACLs to use newer core facilities.

Split uses of admit into admit_ips and admit_hostnames; split def.acl into def.acl_ips and def.acl_hostnames in support of that (but retain def.acl for backwards compability).  Use the escaped version of our domain in the default hostname list; this list is used as regex, so the dots in it are wildcards unless escaped !
Depends on some core changes that actually make admit_ips and admit_hostnames work properly with classic protocol (which previously only knew about admit).
hmm ... yes, looking at the code, hostnames shall work (exact match only), but hostname regexes won't.
Which means we probably need to rethink a bunch of this stuff.  I'll put allowconnects and allowallconnects back to def.acl for now.