weekly release 2.6dev
MDL-25500 lock: New pluggable locking framework.
MDL-25500 locking: Only allow one memcache lock server.

Failover does not make sense for locks because the memcache servers
may not replicate the locks.
Also cleaned up config-dist comments and remove overly escaped slashes.
Hack for locking - Do not keep this commit
The rest
Added storages
Config
MDL-31501 session: Adapt classes for namespace issues
MDL-31501 session: Fixed some coding style issues
MDL-31501 session: Standard driver can use external storages/locks