Common initialiseGLWithSize method

[mcarans]

Remove Windows custom logic
Add one hack for Windows SDL3 pause issue: libsdl-org/SDL#12791 that occurs on some systems eg. when going fullscreen -> window or vice versa
Remove dead code

@phkb Should be almost the same as what you tested but I had to change order of calls for Linux to work

	SDL_SetWindowFullscreen(window, fullScreen);
	if (!fullScreen)
	{
		SDL_SetWindowSize(window, viewSize.width, viewSize.height);
		SDL_SetWindowBordered(window, v_mode);
	}
#if OOLITE_WINDOWS
	else  // Hack for Windows SDL3 pause issue: https://github.com/libsdl-org/SDL/issues/12791
	{     // Occurs on some systems eg. when going fullscreen -> window or vice versa
		LONG currentWindowStyle = GetWindowLong(windowHandle, GWL_STYLE);
		currentWindowStyle &= ~WS_POPUP;
		SetWindowLong(windowHandle, GWL_STYLE, currentWindowStyle);
	}
#endif

[phkb]

Works well from my end.

[mcarans]

@LW-archlinux please can you check it works for you

[LW-archlinux]

Nothing weird noticed with this applied to master.