* PHP-7.4:
  Fix #48725: Support for flushing in zlib stream

When `php_zlib_deflate_filter()` is called with `PSFS_FLAG_FLUSH_INC`
but without new buckets being available (e.g. because a user calls
`rewind()` after writing to the stream), we have to make sure that any
pending data are flushed.  This could basically be done like in the
attached patch[1], but that could cause unnessary flushes, which can be
harmful for compression, and adds unnecessary flush markers to the
stream.  Thus, we use the `php_zlib_filter_data.finished` field, which
has not been used for `zlib.deflate` filters, and properly keep track
of the need to flush.

[1] <https://bugs.php.net/patch-display.php?bug_id=48725&patch=zlib-filter-flush-fix.patch&revision=latest>

Closes GH-6019.

* PHP-7.4:
  Fix #77069: stream filter loses final block of data

Reading from a stream may return greater than zero, but nonetheless the
stream's EOF flag may have been set.  We have to cater to this
condition by setting the close flag for filters.

We also have to cater to that change in the zlib.inflate filter:

If `inflate()` is called with flush mode `Z_FINISH`, but the output
buffer is not large enough to inflate all available data, it fails with
`Z_BUF_ERROR`.  However, `Z_BUF_ERROR` is not fatal; in fact, the zlib
manual states: "If deflate returns with Z_OK or Z_BUF_ERROR, this
function must be called again with Z_FINISH and more output space
(updated avail_out) but no more input data, until it returns with
Z_STREAM_END or an error."  Hence, we do so.

Closes GH-6001.

Closes GH-6250

Closes GH-6173

This should fix most of the remaining issues with tabs and spaces
being mixed in tests.

Closes GH-5958

* PHP-7.4:
  Fix file clash in zlib test