* microsoft visual studio projects added, adds 'make vcxproj' to Makefile

Steps to build Lutro on Windows using Visual Studio:
 - make vcxproj  (requires MSYS2 or make installed for Git BASH)
 - load lutro.sln

You can do these in either order, but the project will fail to load without running make.

Rationale:
 - Provides access to Visual Studio debugging symbols and MSVC debugger.
 - (full stop: this alone was worth all this effort for me)

* Make all the primary target, and fix vorbis build

Co-authored-by: Rob Loach <robloach@gmail.com>