mod_deflate: Handle Zlib header and validation bytes received in multiple
chunks.

PR: 46146, 55666
Submitted by: Yann Ylavic
Reviewed by: ylavic, wrowe, rpluem
Backports: r1572655, r1572663, r1572668, r1572669, r1572670, r1572671, r1573224, r1586745, r1587594, r1587639, r1590509, r1603156, r1604353



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1619753 13f79535-47bb-0310-9956-ffa450edef68