* Fix build with Visual Studio, updating projects to Visual Studio 2019 (as that is what I have installed).
* Changed C++ language standard to C++ 17.
* Add files for in_2sf's spu from Coda's recent commit.
* Add files for zlib now that it is being included as a submodule (removes the need for the zlib DLL as well).
* Remove common.props (due to the aforementioned zlib inclusion as well as the winamp headers also being in the project now).
* Minor NCSF file in the SSEQ player, the check for when to process tracks should've been >=, not >.