Add tests for TreeMap and TreeSet, change TreeSet.add implementation to be
more efficient, fix integer overflow in AbstractSet.hashCode.

Patch by: jat
Review by: scottb (desk review)



git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@2938 8db76d5a-ed1c-0410-87a9-c151d255dfc7