Update irc-info.c to use irc-macros.h

This includes:

 - move IRC_SetPenalty() at the beginning of the handler functions,
 - use macros provided by irc-macros.h,
 - code cleanup.

The main benefits of this patch are core size reduction, streamlined
structure of the handler functions, and enhanced functionality:
because of the _IRC_GET_TARGET_SERVER_OR_RETURN_() macro using the
Client_SearchServer() function, the target of the specific IRC command
can now be given server names, server mask, or the nickname of a user
connected to the server.

Closes bug #153.