UI:

* For new buttons spaces, automatically set horizontal/vertical
  align depending on size, instead of free.

* Cleaned up the UI panel API. There's now a new uiBeginPanel
  function which takes a panel type, and a uiEndPanel which takes
  the final size. uiNewPanel* functions will be phased out.
* Animate the re-alignment when a panel size changes, e.g. when
  enabling dupliframes.

* Load ui scripts from the release/ folder first if it is
  available. This makes it easier to edit ui scripts, since it
  will directly use the original files which avoids having to
  run the build system.
* Improve editing of panel types while blender is open. That
  means fixing some issues with lacking updates, overlaps, strange
  ordering. It even does an animation now when the panel resizes.

source/blender/editors/interface/interface.c

@@ -1688,9 +1688,6 @@ void uiFreeBlock(const bContext *C, uiBlock *block)
 		ui_free_but(C, but);
 	}
 
-	if(block->panel) {
-		block->panel->active= 0;
-	}
 	BLI_freelistN(&block->saferct);
 	
 	MEM_freeN(block);