vout_macosx: don't fail if quartz extreme isn't available, but show a big warning

(cherry picked from commit 3bcac4a47cecf8506de253a53a64eb61e033b0cc)

modules/video_output/macosx.m

@@ -125,9 +125,8 @@ static int Open(vlc_object_t *this)
 
     if( !CGDisplayUsesOpenGLAcceleration( kCGDirectMainDisplay ) )
     {
-        msg_Err( this, "no OpenGL hardware acceleration found, video output will fail" );
-        dialog_Fatal( this, _("Video output is not supported"), _("Your Mac lacks Quartz Extreme acceleration, which is required for video output.") );
-        return VLC_EGENERIC;
+        msg_Err( this, "no OpenGL hardware acceleration found. this can lead to slow output and unexpected results" );
+        dialog_Fatal( this, _("OpenGL acceleration is not supported on your Mac"), _("Your Mac lacks Quartz Extreme acceleration, which is required for video output. It will still work, but much slower and with possibly unexpected results.") );
     }
     else
         msg_Dbg( this, "Quartz Extreme acceleration is active" );