Fix a ton of incorrect behaviour regarding numerics.

- Change m_abbreviation to use ERR_UNKNOWNCOMMAND instead of 420.
- Change m_autoop to use ERR_UNKNOWNMODE instead of 415 which
  conflicted with ERR_BADMASK from RFC 2812.
- Change m_banredirect to use ERR_CHANOPRIVSNEEDED and
  ERR_NOSUCHCHANNEL instead of 690 which conflicted with
  RPL_WHOISLANGUAGE from KineIRCd.
- Change m_cban to use ERR_NOSUCHCHANNEL instead of 384 which
  conflicted with RPL_MYPORTIS from RFC 1459.
- Change m_helpop to use RPL_HELPSTART, RPL_HELPTXT and
  RPL_ENDOFHELP from Charybdis instead of 290 and 292.
- Change m_namedmodes to use RPL_PROPLIST and RPL_PROPEND
  from IRCX instead of 818 and 819.

- Fix the following modules using numbers instead of constants.
  - m_lock
  - m_mlock
  - m_topiclock
  - m_sasl
  - m_silence
  - m_ssl_gnutls
  - m_sslmodes