add failsafe display mode and isUsingFailsafeDisplay() methods for LWJGL
add semicolon
remove isUsingFailsafeDisplay method from Graphics interface
Merge remote-tracking branch 'upstream/master' into failed-display
Merge branch 'master' into failed-display
use callback for display mode creation failure
Merge pull request #2149 from jrenner/failed-display

handle display creation failure for LWJGL
Scene2d: Add positionChanged() method to Actor.
Merge pull request #2184 from ollipekka/premult_alpha

Premultiplied alpha for 2d particle effects
Merge pull request #2183 from GreenLightning/master

Scene2d: Add positionChanged() method to Actor.