Support for resizing windows on all sides
Finished full window resize support

- The main run loop resets the cursor if it falls outside of all windows during a mouse move.
- Added cursors supported by CSS that are not in NSCursor.
- Code cleanup in CPCursor.
- Cursors now indicate available resize directions if there is a window min/max size.
- Reduced slop to 3, what it is in Cocoa.
- Added a second non-min/max window to the demo.
Merge branch 'new-window-resize'
Constrain window resize to usable area of platform window.
Optimisation.
Merge branch 'new-window-resize' into slevenbits
Merge remote-tracking branch 'Slevenbits/master' into slevenbits-master