Make super pass with new test
Closes: http://ironpython.codeplex.com/workitem/33663
(cherry picked from commit 915b8a01a4597a4ef842c0b3fea73ae0942e7ab8)
Fix for cp33720
 - lock non-threadsafe LRU cache before use.

Add test for cp33720
(cherry picked from commit 8772fd3489bf77cfe92b1d78f1e3a4218c4a1bd7)
Importer should use PAL instead of Path APIs
(cherry picked from commit 394408e467bce8ba278e89f8e6f051521388742c)
Remove Silverlight 4 from the build script.