On Roy's suggestion; why wait to try to clear out the input
  stream if it is smaller than MAX_MEM_SPOOL?  Do this upfront
  before dispatching to a body handler.

  This means changing each of the three body pumps to presume
  a preexisting input_brigade was already loaded, so turn around
  their loop conditions.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@219224 13f79535-47bb-0310-9956-ffa450edef68