Merge r1572655, r1572663, r1572668, r1572669, r1572670, r1572671, r1573224, r1586745...

Merge r1572655, r1572663, r1572668, r1572669, r1572670, r1572671, r1573224, r1586745, r1587594, r1587639, r1590509 from trunk.

Commit 1 on 6 to fix reentrance (incomplete Zlib header or validation bytes) in mod_deflate's output and input filters.
PR 46146 (patches from duplicated PR 55666)

Handle Zlib header buffering in the inflate output filter :
- add the new deflate_ctx_t fields needed to re-enter the Zlib header parsing,
- introduce the new consume_zlib_flags() function to parse/consume the ZLib flags (will be used by the other filters too),
- use it to handle incomplete header in the output filter (deflate).

This alone fixes PR 55666, but the issue remains for PR 46146 (inflate/deflate input filters), hence the following patches.

Commit 2 on 6 to fix reentrance (incomplete Zlib header or validation bytes) in mod_deflate's output and input filters.
PR 46146 (patches from duplicated PR 55666)

Handle Zlib header buffering in the inflate input filter :
- loop until all the header is received,
- handle non blocking reads returning empty brigade,
- fix a double ap_get_brigade() when an EOS brigade is encountered while reading the header,
- in that case and no data was received so far, don't return an error but SUCCESS with the EOS, otherwise fail,
- don't remove the Content-Length and Content-MD5 headers until some data is read.

Still does not handle Zlib flags for now, next commits.

Commit 3 on 6 to fix reentrance (incomplete Zlib header or validation bytes) in mod_deflate's output and input filters.
PR 46146 (patches from duplicated PR 55666)

Handle Zlib validation bytes buffering (CRC + length) in the inflate input filter :
- use validation_buffer and validation_length as state,
- loop until all the bytes are received.

Commit 4 on 6 to fix reentrance (incomplete Zlib header or validation bytes) in mod_deflate's output and input filters.
PR 46146 (patches from duplicated PR 55666)

Handle non blocking reads which would block in the inflate input filter (not an error).

Commit 5 on 6 to fix reentrance (incomplete Zlib header or validation bytes) in mod_deflate's output and input filters.
PR 46146 (patches from duplicated PR 55666)

Handle Zlib flags in the inflate input filter as in the output filter, using consume_zlib_flags().

Commit 6 on 6 to fix reentrance (incomplete Zlib header or validation bytes) in mod_deflate's output and input filters.
PR 46146 (patches from duplicated PR 55666)

Ignore empty buckets and split buckets longer than INT_MAX (since zlib uses 32-bit ints only) in all filters.

mod_deflate: when consuming zlibs flags, APR_INCOMPLETE implies no more bytes available.

mod_deflate: update empty log tags.

mod_deflate: Delay INFLATE input filter's self removal until all the buffered
             buckets are out (including EOS). PR 46146.

mod_deflate: Don't return gzip-ed data when reading FLUSH bucket in INFLATE
             input filter, forward the FLUSH but keep reading should EOS/more
             follow (should not happen, but mod_deflate won't fix it).

mod_deflate: follow up to r1587639.
Don't break the looped brigade when moving the FLUSH bucket to the returned bb
and continue reading.

Reviewed by: ylavic, jim, covener

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1604458 13f79535-47bb-0310-9956-ffa450edef68