Bugfixes from own collection:

- when renderwin exists, but not used for render, the ESC timer check still
  could return ESC event, due to missing flag clearing.
  (For example in sequencer, a scene strip did not update on frame advance)

- option 'single layer' set in combination with render "Do Sequence" didn't
  free the pushed layers.

source/blender/src/sequence.c

@@ -903,7 +903,7 @@ static void do_build_seq_ibuf(Sequence * seq, int cfra)
 				if(G.rendering)
 					re= RE_NewRender(" do_build_seq_ibuf");	
 				else
-					re= RE_NewRender(seq->scene->id.name);
+					re= RE_NewRender(sce->id.name);
 				
 				/* prevent eternal loop */
 				doseq= sce->r.scemode & R_DOSEQ;