[Ur] New release

[Adam Chlipala]

Available as usual at: http://www.impredicative.com/ur/

CHANGELOG for this release:

- Client-side mouse and keyboard event handlers are now functions over 
records.
- More flexibility in local type class instances
- Remove 'class' declaration; use 'con' instead now.
- SQL window functions
- New HTML pseudo-tag: <active>
- New Basis members: getenv (and associated functions), giveFocus
- New Top member: postFields (to process POST form data when called by 
some external script)
- HTTP daemons take '-a' option to set IP address to listen on
- More global mouse event hooks
- Bug fixes and performance improvements