Windows compatibility fixes 

It is not always possible to ship the Visual Studio redistributable packages. This is one of the reasons why companies like ActiveState tend to build their perl/python distributions with older compilers, notably the Windows 2003 platform SDK.

This PR adds (mostly) fallback support to the Windows portability layer, that is, uses the not-so-secure versions if the secure version is not available. I've had a few requests to get ```Git::Raw``` (perl bindings) to successfully build with ActivePerl as deployment environments don't have compilers installed and/or its not feasible to build it externally.