Add a couple of optimizations to the priority queue code:

 * bubble_up and percolate_down do not need to do "swaps" -- they can just
   shift the existing items and reinsert the moving item once at the end
 * minchild() did not need that for loop -- a node can only ever have at
   most two children, and they are guaranteed to be adjacent


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@96089 13f79535-47bb-0310-9956-ffa450edef68