Tests for F# 3.0 (F#3.1 back port)

This should be the back ported F# 3.1 tests made available for F# 3.0

I have added `#if FSHARP_31` to all the tests that are not available to F# 3.0 based on the test suite that was released.  This is from the context of **only** the tests that made cross platform e.g. The tests running from [here][ossTestSuite].

I can remove all of the currently unused tests that are not enabled for cross platform use if that is preferable.

[ossTestSuite]: https://github.com/7sharp9/fsharp/blob/master/tests/fsharp/core/run-all.sh