Added missing method for SL and WinRT.

ConvertAll does not exist as a method on the List<T> for the above platforms,
so the builds for them fail.
INCR to v3.9.44
New SL5 binaries for 3.9.44.

To be used with the next NuGet package.
Merge pull request #314 from ddotlic/master

Latest SL5 fixes __and__ 3.9.44 binaries for SL5