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-7.2:
  Fixed bug #76044 'date: illegal option -- -' in ./configure on FreeBSD

* PHP-7.1:
  Fixed bug #76044 'date: illegal option -- -' in ./configure on FreeBSD

Seems it only defines __builtin_cpu_supports but no __builtin_cpu_init
(Apple LLVM version 9.0.0 (clang-900.0.38))

* 'master' of git.php.net:/php-src: (37 commits)
  Avoid conditions inside loop
  Improve loop vectorization
  Improve loop vectorization
  Remove unused function
  Fixed bug #75938
  Remove unused files
  Fixed bug #75940 Unnecessary compile wrapper with PHP_THREAD_SAFETY=yes
  typo
  Update README.GIT-RULES
  Fix SKIPIF section
  Fixes bug #75871 Use pkg-config for libxml2 if available
  Fixed bug #49876 lib path on 64bit distros
  Refactor testing READMEs
  Fixed bug #65414
  Fixed bug #65414
  Fixed bug #74519 strange behavior of AppendIterator
  fix #74519 strange behavior of AppendIterator
  Use bool instead of boolean
  Remove space between function name and open parentheses
  Fix some misspellings
  ...