Fix 63 character hostname truncation.

Hostnames with exactly 63 characters were being truncated to 62
characters since register_user was using strncpyzt incorrectly.

The size given to strncpyzt should be the total size of the destination
buffer including the terminating '\0' character. register_user was using
HOSTLEN for the size instead of HOSTLEN + 1.

Also fix some other code that got this wrong.

Signed-off-by: epiphani <epiphani@dal.net>
Merge pull request #9 from DALnet/master

SVSTAG & CMODE +A (Auditorium mode)
Merge branch 'master' of ssh://github.com/epiphani/bahamut
Auditorium mode fixes (cmode +A)
Hide quits and nick changes as well.

-Kobi.