Window improvements - Githubissues

Changes:

Added some stuff from SOC's Magic library in include\magic.h (RenderCore)
D3D9 device reset when resizing the window (removes stretching)
MaintainAspectRatio option with custom border image (image thanks to @End-User-Person)
Alt+Enter for fullscreen
Alt+F4 proper implementation
Multiple monitors support
DisableExitPrompt option to remove the annoying message
DPI-Aware Mod Manager and other minor improvements
Moved window stuff to a separate source file
Fix a potential crash in the WndProc code, though the loader takes control a bit late anyway

Note: menus are hardcoded for 4:3 and 16:9 and will not work properly for other aspect ratios

X-Hax / sa2-mod-loader