Irc: demote unknown user errors in parseModes() to DEBUG
Irc: demote unknown user errors in parseModes() to DEBUG

Some ancient services like Anope 1.8 set SVS2MODE +d on users when they connect, even if the user quits right after. Due to lag we may receive the MODE after the QUIT instead of before.

(cherry picked from commit ec4e71c8cfb86105a28e7bc0b63d91dcc8c37a60)

GLolol/PyLink