Prepare to backport r209836 whitespace changes; this is the one
  minor code change to declare *buf once, obliterating the need for
  a number of code blocks throughout this function.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/proxy-reqbody-2.0.x@230704 13f79535-47bb-0310-9956-ffa450edef68