Clarify NickServ REGISTER help messages; fix ?raw and ?dump errors.

Clarify NickServ REGISTER help messages; fix ?raw and ?dump errors.

src/nickserv.help (REGISTER): Rephrase the message about using the
same password to hopefully make it clearer.

src/opserv.c (cmd_dump, cmd_raw): Use local buffers to hold the
original message, so that parse_line() will not unsplit the line into
the "original" buffer and strip out the sentinel :.
git-archimport-id: srvx@srvx.net--2005-srvx/srvx--devo--1.3--patch-19