add failsafe display mode and isUsingFailsafeDisplay() methods for LWJGL

I ran into a problem where I was populating a list of desktop resolutions in an options menu using the getDisplayModes method and some resolutions caused a crashed on startup (despite supposedly being supported, probably a fullscreen issue).

This PR allows a failsafe mode for creating a (windowed, non-fullscreen) display mode if the first one fails.  The default settings have it disabled, so it will not cause unexpected confusion from silent failures and recoveries.

like setTitle(), it is only applicable for desktop, but is this case only LWJGL.  I don't really see the need for it on JGLFW.

This allows something like this in the create method:
```java
if (Gdx.graphics.isUsingFailsafeDisplay()) {
			PopUpMenu.show("Using failsafe display settings! Please change resolution in Options menu!");
		}
```