Added support for JOIN, QUIT, PART, NICK in the IRC bridge

- It'll now show messages such as:
  [ #irc ] User IRC.<nick> joined the channel.
  [ #irc ] User IRC.<nick> left the channel. [Quit: <quit message>]
  [ #irc ] User IRC.<nick> left the channel. [<leave message>]
  [ #irc ] User IRC.<old nick> is now known as IRC.<new nick>"
- To disable, comment out the respective entries in irc_bot_init.

Signed-off-by: Haru <haru@dotalux.com>
Added support for CTCP commands to the IRC bridge

- Implements relevant parts from the CTCP specification at
  http://www.irchelp.org/irchelp/rfc/ctcpspec.html
- Fixed parsing of CTCP VERSION requests (follow-up to 19b8cbb)
- Added support for new CTCP commands:
  - ACTION (also known as /me command): will be shown to players in the
    #irc channel as "[ #irc ] * IRC.<nick> <action message> *"
  - ERRMSG, FINGER: are silently ignored (irrelevant or deprecated)
  - PING is replied to with the correct pong reply
  - TIME is replied to with the current server time

Signed-off-by: Haru <haru@dotalux.com>
Small IRC bridge tweaks

- Added documentation for the remaining undocumented functions
- Dropped unused function ircbot->join
- Moved commented out debug commands to ifdef blocks; to quickly toggle
  them, (un)comment #define IRBCOT_DEBUG on top of irc-bot.c

Signed-off-by: Haru <haru@dotalux.com>
Added support for long IRC messages

- IRC messages are no longer truncated to one line of client chat
  message, if they are longer than that.  They're instead posted as
  multiple lines. (See comments in the source to disable this, if you
  wish to.)
- Added a define for the max acceptable IRC message length, and
  increased the size of send_string to fit it

Signed-off-by: Haru <haru@dotalux.com>
Added support for Nick Server GHOST command

Credits to Yommy for the idea

Signed-off-by: Haru <haru@dotalux.com>