Speed patched binary, resolution option for windowed mode, and a few other improvements

[fullstea...@gmail.com]

Building on some of mefistotelis' work, I've forked the original source and have created two releases:

- A Windows binary that includes the speed patch and fixes the crash bug when saving: https://github.com/leonsodhi/swars/releases/tag/swars-0.3.1

- A Windows binary that adds:

• Fullscreen borderless windowed mode
  
• Resolution switch for windowed mode
  
• Mouse lock fix to keep the mouse inside the window
  
• Monitor switch for multi-monitor setups
  

Given the number of changes, this release is experimental but has been working well for me. For the latest pre-release version, see: https://github.com/leonsodhi/swars/releases

For those that would prefer to build their own binaries, instructions for the original source and my forked copy are included in the README: https://github.com/leonsodhi/swars/blob/master/README.md

I haven't attempted to build either release for Linux or OS X, but the biggest change was porting the code to SDL2 so if there are problems they may not be too difficult to fix.