Found and fixed a memory leak bug while inspecting the code.

Details at http://xstream.10960.n7.nabble.com/FastStack-and-GC-tp300.html

Methods from class 'FastStack' don't nullify references
http://jira.codehaus.org/browse/XSTR-264

Contributed the PassiveTimeOutMap class.

This is a Map decorator which passively evicts expired keys once their expiry time has been reached.

When putting a key-value pair in the map, this decorator calls expiryTime(key, value), passing the key and the value as parameters, and uses the returned value as the expiry time for that key.

When getting the value for a key, its expiry time is checked, and if it's greater than the current time, the value is returned. Otherwise, the key is removed from the decorated map, and null is returned.

Doing so, there's no need to have a separate, active thread (hence the name 'passive') to check expiry times - the check is performed on demand.

See https://issues.apache.org/jira/browse/COLLECTIONS-241

Contributed with improvement suggestions and Python code.

See https://github.com/rethinkdb/rethinkdb/issues?q=+author%3Aelifarley+

Primary developer

I've made some improvements to the ACL extension, like:

* support for 'pretxncommit', so that one can call the ACL hook at pre-commit time too. This is useful because now it's possible to avoid violating ACL permissions much sooner, at commit time, instead of waiting for a PUSH to check if there were any invalid commits.

* support for 'everybody ' (using an asterisk) in user list

* support for branch-based access control;

* support for OS-level groups using @group syntax;

* support for group definitions in section [acl.groups], which take precedence over OS-level groups;

See commits at http://selenic.com/hg/log?rev=elifarley

See also: https://www.openhub.net/p/mercurial/contributors/21363167334044