Followup r94754: move protocol expansion from getIRCLine() to inside getInternalUrl...

Followup r94754: move protocol expansion from getIRCLine() to inside getInternalUrl(); these internal URLs should always be fully qualified. Effectively this means that if $wgServer is protocol-relative and $wgInternalServer either isn't set or is also protocol relative (but it really shouldn't be the latter!), we'll add  to URLs used for Squid purging and in IRC lines. If people want those to be https:// instead, they can set $wgInternalServer accordingly.

We should really, really break the connection between internal URLs used for Squid purges and URLs used for IRC, and use the latter in e-mails as well. This was briefly discussed in the CR comments on r44412 and I'll be working on that today.