Add clipping support for the Silverlight version.
Add clipping support for the Silverlight version.

Thanks to maitredede for the patch.

git-svn-id: 6ad24f2065037e4a655044d9aca5e448f7518dcb@68 fd59bba8-8519-0410-9389-e36bf2bdbbd6

masshabit/explorercanvas