Fix DateTime regression on ARM

Fix DateTime regression on ARM

This is the same issue as in https://github.com/mono/referencesource/pull/7,
i.e. there's an overflow when casting a too large value from double->long
and the referencesource implementation relies on this being a large negative
value in order for the ArgumentOutOfRangeException to be properly thrown.

As Mono's runtime on ARM in this case returns -1, the exception isn't thrown.

The fix is to introduce an explicit overflow check, catch an eventual
OverflowException and raise the proper exception instead. This can be JIT'd
to better code than checking if the value fits into long every time.

It fixes a couple of DateTime unit tests that currently fail on ARM.