* When configuring extensions, considers the PHPDBG SAPI as CLI thus
  allowing e.g. to have the pcntl extension available within PHPDBG.

Signed-off-by: Samuele Kaplun <kaplun@protonmail.com>

Makefiles for PHP extensions generated by phpize expect the PHP_MODULES
to contain a list of libtool .la files so that it can read the $dlname
variable from them by sourcing them in to a shell. On AIX, the code was
setting PHP_MODULES to a list of .so files, which meant the dlname was
blank, preventing the tests from being able to run.

Change the AIX code path in the PHP_SHARED_MODULE macro to match the
output on other platforms, using libtool .la files.

* PHP-7.1:
  Rename var

* PHP-7.1:
  Fixed bug #76153 Intl compilation fails with icu4c 61.1

Additionally, ICU >= 59.1 requires C++11, so add the flags. Some
refactoring is needed to comply with the latest recommended build
options, such as automatic icu namespace addition.

As described in bug report #75722, the configure script (acinclude.m4)
currently searches for the valgrind header file and enables valgrind
support if found.

When cross-compiling the searched paths are invalid for the target
platform because they belong to the host system. At the moment, there is
no way to tell the build system a dedicated path where to look for the
header file.

This leads to the issue, that when cross-compiling eg. for ARMv5 platform,
that valgrind header file is detected - e.g. because host system is amd64 -
and support is enabled - but target platform will never support valgrind
(valgrind requires e.g. at least ARMv7).

This change reworks the detection so that user could manually opt-in
valgrind support and optionally specify a directory where the build system
should look for the header file using the --with-valgrind option.

* PHP-7.1:
  Fixes bug #75871 Use pkg-config for libxml2 if available