Do not allow a topic change if a user may not send to the channel (resv, cmode +m, cmode +b, cmode +q, etc.).
This is only checked for local users.
For optimal compatibility, a failure for this reason still returns ERR_CHANOPRIVSNEEDED.
Side effect: normal users cannot change topics of resv'ed channels, even if they have ops, just like they already cannot send messages. This only matters if resv_forcepart is disabled, as the user would have been removed from the channel otherwise.