Remove backported entry (see r1684515)

     problems if used with round robin load balancers). Don't regenerate the

     secret on graceful restarts. PR 54637  [Stefan Fritsch]

  *) core: Remove apr_brigade_flatten(), buffering and duplicated code

     from the HTTP_IN filter, parse chunks in a single pass with zero copy.

     Reduce memory usage by 48 bytes per request. [Graham Leggett]

  *) core: Stop the HTTP_IN filter from attempting to write error buckets

     to the output filters, which is bogus in the proxy case. Create a

     clean mapping from APR codes to HTTP status codes, and use it where