[PATCH] fix idr_get_new_above id alias bugs

[Hoang-Nam Nguyen]

> With this patch, idr.c should work as advertised allocating id
> values in the range 0...0x7fffffff.  Andrew had speculated that
> it should allow the full range 0...0xffffffff to be used.  I was
> tempted to make changes to allow this, but it would require changes
> to API, e.g. making the starting id value and the return value
> unsigned.
Hi Jim, thanks much for this patch. It should work fine as far
as I can read. Will give it a try in next couple of days.
Nam