offchannel fixes; more memory verification

offchannel fixes; more memory verification

src/chanserv.c (cmd_register): Do not join channels if the default
options include being offchannel.

src/common.h: Verify list allocations when appending or removing.

src/hash.c (GetUserMode): Verify channel and user list allocations.

src/log.c (log_entry_search): Keep pointer to last visited log entry.

src/proto-p10.c (mod_chanmode_parse): Fail if trying to change +z when
passed MCP_REGISTERED.
git-archimport-id: srvx@srvx.net--2005-srvx/srvx--devo--1.3--patch-9