relay: mangle the mode name when forwarding extban->cmode so that +b syntax filters don't trigger
relay: mangle the mode name when forwarding extban->cmode so that +b syntax filters don't trigger

This should allow bidirectional forwarding between UnrealIRCd +b ~T:block:<glob> and InspIRCd +g <glob> to work.
(#557)

GLolol/PyLink