The acinclude.m4 file is in a usual Autotools build processed with
Automake's aclocal tool. Since PHP currently doesn't use Automake and
aclocal this file can be moved into the build directory. PHP build
system currently generates a combined aclocal.m4 file that Autoconf
can processes automatically.

However, a newer practice is writing all local macros in separate
dedicated files prefixed with package name, in PHP's case PHP_MACRO_NAME
and putting them in a common `m4` directory. PHP uses currently `build`
directory for this purpose.

Name `php.m4` probably most resembles such file for PHP's case.

PHP manually created the aclocal.m4 file from acinclude.m4 and
build/libtool.m4. Which is also not a particularly good practice [1], so
this patch also removes the generated alocal.m4 usage and uses
m4_include() calls manually in the configure.ac and phpize.m4 files
manually.

- sort order is not important but can be alphabetical
- list of *.m4 files prerequisites for configure script generation
  updated
- Moving m4_include() before AC_INIT also removes all comments starting
  with hash character (`#`) in the included files.

[1] https://autotools.io/autoconf/macros.html

With recent transition to pkg-config/pkgconf this macro has been now a
simple wrapper for PKG_CHECK_MODULES and PHP_EVAL_INCLINE so it's better
to omit it altogether and use these two in the *.m4 code directly.

Added ".tbd" extension support for libiconv on Mac to use
CommandLineTools SDK shared library.

readdir_r() is deprecated in modern glibc versions. readdir() is
thread safe in practice, as long as there are no concurrent accesses
on the *same* directory stream.

This patch refactors these macros to also checks for the required given
versions of bison and re2c.

- PHP_PROG_RE2C and PHP_PROG_BISON take optional args - minmimum version
  required, and bison also excluded versions.
- Instead of caching values this uses manual checking and messaging
  outputs.
- It looks like the minimum version of RE2C 0.13.4 is working ok so far.

The genfiles script improvements:
- Add make override in genfiles
- Move checkings from makedist to genfiles
- Refactored output messages
- Various minor enhancements

* PHP-7.3:
  Consider phpdbg as cli

* PHP-7.2:
  Consider phpdbg as cli

* 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>