On stable versions, bring back the TRUE/FALSE defines by defining
_U_DEFINE_TRUE_AND_FALSE.

Closes GH-6397.

As of commit 81b2f3e[1], `parse_url()` accepts URLs with a zero port,
but does not report that port, what is wrong in hindsight.

Since the port number is stored as `unsigned short` there is no way to
distinguish between port zero and no port.  For BC reasons, we thus
introduce `parse_url_ex2()` which accepts an output parameter that
allows that distinction, and use the new function to fix the behavior.

The introduction of `parse_url_ex2()` has been suggested by Nikita.

[1] <http://git.php.net/?p=php-src.git;a=commit;h=81b2f3e5d9fcdffd87a4fcd12bd8c708a97091e1>

Closes GH-6399.

As mentioned on bug #80171. This one is in libtool.m4, might get
lost on libtool updates.

Patch contributed by Alexander Bergmann.

Closes GH-6389.

In this function, `i` is of type `size_t`.

Unless `SQLGetData()` returns `SQL_SUCCESS` or `SQL_SUCCESS_WITH_INFO`,
the `StrLen_or_IndPtr` output argument is not guaranteed to be properly
set.  Thus we handle retrieval failure other than `SQL_ERROR` by
yielding `false` for those column values and raising a warning.

Closes GH-6281.

Using a cloned finfo object will crash.

This reverts commit bf6873a18e3b6b00f82a645c0893a281ae8eadb8.

CVE-2020-26159 is bogus; the "bug" was apparently a false positive
reported by Coverity, and the "fix" apparently wrong, see
<https://github.com/kkos/oniguruma/issues/221>.

Closes GH-6357.

libxml2 has no particular issues parsing HTML strings with NUL bytes;
these just cause truncation of the current text content, but parsing
continues generally.  Since `::loadHTMLFile()` already supports NUL
bytes, `::loadHTML()` should as well.

Note that this is different from XML, which does not allow any NUL
bytes.

Closes GH-6368.