[Ur] New release

[Adam Chlipala]

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

CHANGELOG for this release:

- Compatibility fixes for new Automake and GCC versions
- Allow synchronous RPC's in 'onunload' code
- Start of special cases for parsing CSS class names: interpret "table" 
as identifier 'tabl'
   (since 'table' is an Ur/Web keyword)
- Bug fixes and improvements to type inference and optimization