Create and archive PDB files for Windows builds

As per discussion on email, we want to ensure that Windows issues can be debugged efficiently, which requires that we:

1. Select "Release with Debug Info"- this will create PDB files during the build.
2. Save the relevent PDB files (memcached.pdb, ep.pdb, etc) somewhere.

To actually debug after the fact (on say a different machine) you need:

a) The original .exe / .dll files from the build (which are packaged up already).
b) The aforementioned PDB files (in any path).
c) Matching source (in any path) - which we can checkout using the informaiton in the manifest.