Added some locking to RecentlyUsedContainer
Added some locking to RecentlyUsedContainer

Almost all use of access_log is now synchronized with a lock.

Solves at least the worst thread safety problem.
That is, _prune_invalidated_entries as long a no one external changes
access_log.

luca3m/urllib3,sileht/urllib3,matejcik/urllib3,denim2x/urllib3,Disassem/urllib3,Geoion/urllib3,sigmavirus24/urllib3,gardner/urllib3,t-8ch/urllib3,asmeurer/urllib3,tutumcloud/urllib3,sornars/urllib3,msabramo/urllib3,boyxuper/urllib3,asmeurer/urllib3,urllib3/urllib3,msabramo/urllib3,mikelambert/urllib3,Lukasa/urllib3,tutumcloud/urllib3,urllib3/urllib3,Geoion/urllib3,Disassem/urllib3,Lukasa/urllib3,mikelambert/urllib3,gardner/urllib3,haikuginger/urllib3,matejcik/urllib3,denim2x/urllib3,silveringsea/urllib3,silveringsea/urllib3,boyxuper/urllib3,t-8ch/urllib3,sornars/urllib3,sigmavirus24/urllib3,haikuginger/urllib3,luca3m/urllib3,sileht/urllib3