Currently, we do not send last-modified headers for the RC if patrolling is in use...

Currently, we do not send last-modified headers for the RC if patrolling is in use, since that messes with the way we determine if the RC has changed. Change it to not send those headers only if using RC patrol, and the current user can
see patrol marks.

As an aside, Special:Recentchanges does not show new page patrol marks
if $wgUseNPPatrol = true, but $wgUseRCPatrol=false (it only shows them if
both are true), where Special:newpages shows patrol stuff whenever $wgUseNPPatrol
is true, regardless of $wgUseRCPatrol. Which is a tad weird, but whatever.