Merge remote-tracking branch 'alexis/various-fixes-for-games'

Latest additions to the standard library for Round'n Round.

The Float::abs implemetation corrects a bug present in master.

diff --cc lib/mnit_linux/linux_opengles1.nit
Simple merge

diff --cc lib/mnit_linux/sdl.nit
index d77a08c,8dfe561..527624a
--- 1/lib/mnit_linux/sdl.nit
--- 2/lib/mnit_linux/sdl.nit
+++ b/lib/mnit_linux/sdl.nit
@@@ -127,9 -136,9 +136,9 @@@ extern SDLDisplay in "C" `{SDL_Surface 
                                                   event.motion.x, event.motion.y);
        #endif
  
 -                                      return SDLMouseMotionEvent_as_nullable_InputEvent(
 +                                      return SDLMouseMotionEvent_as_nullable_IE(
                                                        new_SDLMouseMotionEvent( event.motion.x, event.motion.y,
-                                                               event.motion.xrel, event.motion.yrel ) );
+                                                               event.motion.xrel, event.motion.yrel, SDL_GetMouseState(NULL, NULL)&SDL_BUTTON(1)) );
  
                                case SDL_MOUSEBUTTONDOWN:
                                case SDL_MOUSEBUTTONUP: