SERVER-14350 validate distances for circular regions in $near/$within
(cherry picked from commit 7a0d83d88d18d5c28fe13bd5dc0b13d1c6c2ef22)
SERVER-12750 disallow exhaust query option through mongos
(cherry picked from commit 98fb05b9cc74318984574478cc7eadc1167a97e8)
Merge remote-tracking branch 'upstream/v2.6' into v2.6