Fix Win32 build problems

Michael,

I've had a few emails in the past months about build failures on Windows. This PR should fix them for most newer VS versions. I don't have versions older than 2012 with which to confirm.

- Updates config.h.win32 to match config.h.in (I tried my best to get the `PACKAGE_*` details correct)
- Adds json_config.h.win32
- Adds include required for `InterlockedCompareExchange` in linkhash.c
- Updates old VS project to copy json_config.h.win32 to json_config.h
- Adds VS2k13 project

The project now builds, although with numerous warnings about "insecure" API's. Let me know if you'd like me to push a commit which adds `_CRT_SECURE_NO_DEPRECATE` to suppress these warnings.