(GH-531) Fix - Powershell v2 fails to download SSL v3 files

Powershell, which uses the .NET Framework v2, has a bug that prevents it from
falling back to SSL3 when TLS doesn't properly download files. So it causes the
response to timeout because it never receives a response.

This forces the security protocol to SSL3 when using Poshv2.
Merge remote-tracking branch 'upstream/stable'