The `PREFIX` key in `ISUPPORT` (usually) takes the form
`(modes)prefixes` e.g. `(ov)@+`. The current implementation will
therefore set `serv->nick_modes` to a string like `"(ov"` instead
of the desired `"ov"`. This causes the nick list to not properly
update with which users have which prefix modes. Skip over the
initial `'('` so we capture the correct modes and fix that issue.