Windbg support

[emeryberger]

This PR adds support for WinDBG (windbgx.exe).

0. Install vcpkg: Follow instructions here if vcpkg is not installed already.
1. Navigate to the src\chatdbg directory: cd src\chatdbg
2. Install needed dependencies: Runvcpkg install
3. Build the chatdbg.dll extension: Runmkdir build & cd build & cmake .. & cmake --build . & cd ..

Using ChatDBG:

• Load into WinDBGX:
  • Run windbgx your_executable_here.exe
  • Click the menu items View -> Command browser
  • Type .load build\debug\chatdbg.dll
• After running code and hitting an exception / signal:
  • Type !why in Command browser

[nicovank]

I have no access to a Windows machine until Sunday evening, will try this out then.

[emeryberger]

I think it's in good shape, merging, post-merge review welcome :).