Remove CUser::m_bIRCConnected

Remove CUser::m_bIRCConnected

CUser::GetIRCSock() != NULL is the replacement. This is a small chance in
sematics. Before this, a user only counted as connected to IRC when the 001
numeric was received. Now it already counts as connected when the connection
was established. This change doesn't hurt any of the current users of
CUser::IsIRCConnected() and so this change should be fine.

Yay, one var less ;)

git-svn-id: https://znc.svn.sourceforge.net/svnroot/znc/trunk@1131 726aef4b-f618-498e-8847-2d620e286838