mod_ssl: Extend the coalescing filter to avoid sending HTTP response
headers in a separate TLS record to the response body in some cases.

* modules/ssl/ssl_engine_io.c:
  Increase size of coalesce buffer to AP_IOBUFSIZE (8Kb).
  (ssl_io_filter_coalesce): Try harder to fill the prefix which
  gets coalesced, including a read&split of a morphing bucket type

Github: closes #106


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1875871 13f79535-47bb-0310-9956-ffa450edef68
