Remove extra magnitude from magic texture mapping values

- These used to be fixed point, but now they're floating point, so the
  excess magnitude is unneeded.
Remove DepthScale and DepthOrg from FWallTmapVals
- Ported SDL backend to SDL 2.0. Still needs a little bit of polish, but it works.
- Enabled vid_vsync for SDL2 although just turning it on doesn't perform right.
- Improved fullscreen a bit.
- Removed XCursor code since SDL2 has proper color cursor support.
- Improved international keyboard support by falling back to scan codes if we don't recognize a keycode.
- Clear out any residual mouse movement when entering relative mouse mode.
- Improve letterboxing in fullscreen by taking into account animorphic ratio settings.
- Added more resolutions to the hard coded table (up to 5K).
- Since we're using scaling for fullscreen, we should probably just use the hard coded table for fullscreen resolutions as well.
- Fixed: Resolution menu used fake aspect ratio to determine which aspect to file a resolution under.
- Added a way to use SDL surface blitting instead of accelerated textures.
- Adapt SDL2 changes for the Mac (both using SDL2 backend and Cocoa).
Removed no longer used SDL wrapper functions from OS X native backend
Added several missing video resolutions

All feasible display dimensions are in the list except with 21:9 aspect ratio
Merge pull request #187 from alexey-lysiuk/sdl2_add

[SDL2] Minor fixes and cleanup
OS X native backend no longer use files from src/sdl directly

Cocoa backend is compiling but failed to link
Some files are referenced using symbolic links
Apple's HID Utilities were moved to own directory
Get rid of SDL in more parts of native OS X backend
Video part of native OS X backend as a copy-paste of SDL one

Dependency from SDL still exists, pending major refactoring
Rearranged files to avoid usage of symbolic links
Merge branch 'master' of https://github.com/rheit/zdoom into z_osx_pure
Added missing #include
Removed unnecessary SDL #include's
No more SDL dependency in native OS X backend
Fixed path to SDL specific Obj-C++ file
Native OS X backend no longer requires SDL