Merge r709666 from trunk:

* Use distinct char pointers for sending and receiving buffers to avoid
  destroying the pointer to the sending buffer in the ajp message if
  data is received from the backend before all data is sent to the
  backend.

PR: 45911

Submitted by: rpluem
Reviewed by: rpluem, jim, jfclere


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@714273 13f79535-47bb-0310-9956-ffa450edef68