Fix window resize/maximize

[Raptor007]

Resizing or maximizing the window seems to miss the SDL2 event(s) that should signal the game to resize its contents.

It might also be nice for the maximize button and/or alt+enter to toggle fullscreen mode.

[Raptor007]

You can work around this bug in the console or settings.cfg.
To change window size:

g_res_windowed_x 1920
g_res_windowed_y 1080
g_restart

To change to fullscreen mode:

g_fullscreen true
g_restart

[Raptor007]

The problem is here: https://github.com/Raptor007/RaptorEngine/blob/master/Core/RaptorGame.cpp#L392

if( event.type == SDL_WINDOWEVENT_RESIZED )
	Gfx.SetMode( event.window.data1, event.window.data2 );

Apparently SDL_WINDOWEVENT_RESIZED is a window event subtype, not an event type, so it never matched.
New code for BTTT v0.9.9:

if( event.type == SDL_WINDOWEVENT )
{
	if( (event.window.event == SDL_WINDOWEVENT_RESIZED) && ! Gfx.Fullscreen )
		Gfx.SetMode( event.window.data1, event.window.data2 );
	else if( (event.window.event == SDL_WINDOWEVENT_MAXIMIZED) && Cfg.SettingAsBool("g_maximize_fullscreen") )
		Gfx.SetMode( 0, 0, Gfx.BPP, true, Gfx.FSAA, Gfx.AF, Gfx.ZBits );
}

Also, since SDL2 does not destroy the OpenGL context upon window resize, I've patched Graphics::SetMode( x, y ) so it'll just change the resolution-related variables without restarting graphics.