Dispatch of KeyPress event throws a System.AccessViolationException

[AzuxirenLeadGuy]

Issue description

While running a RenderWindow instance, any KeyPress event results in throwing a System.AccessViolationException.

How to reproduce

Run the example project in example/window, and press any key

Expected behaviour

The key is processed by the event successfully

Actual behaviour

An uncaught exception interrupts the program, with the following message on the console.

Press ESC key to close window
Fatal error. System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
   at SFML.Window.WindowBase.CallEventHandler(SFML.Window.Event)
   at SFML.Window.WindowBase.DispatchEvents()
   at window_core.SimpleWindow.Run()
   at window_core.Program.Main(System.String[])

[uwaaya]

this is a serious heisenbug in SFML.Net. it cant usually be replicated while debugging but it appears in release builds.
the new ScanCode field of CSFML 2.6 wasnt accounted for in Event or KeyEvent, and inconsequentially KeyEventArgs. the total size of CSFML events is now 28 bytes. adding the field to KeyEvent and updating the size of the Event struct fixes this crash.

[uwaaya]

its also worth mentioning that this same bug may cause KeyEvent to not report correct values (i have not tested this), so fixing it will kill two birds with one stone

[eXpl0it3r]

It might be recommended to stick to CSFML 2.5.2 until SFML.Net has been updated for 2.6

[uwaaya]

if its any consolation, this is the only problem with SFML.NET which we could find.
we patched this bug in our internal fork of SFML.NET (currently 321101d) with CSFML 2.6, and have been essentially field testing it for over a week. we have not discovered any further problems from upstream besides this one.