Is SYNC_CLOCK used?

[gvissers]

An incoming SYNC_CLOCK message from the server makes the client calculate the difference between the timer tick on the server, and that on the client. This information is then never used in the client. It's hard to come up with a use for it anyway, offsets depend on when the server or client starts, and clocks will drift.

Hmm, looks like a SYNC_CLOCK message calls ERR() with EXTRA_DEBUG enabled anyway. Is it deprecated? Could we remove it, or ignore it?