Change $SED to "${SED}" such that the IFS is not used to split the
output of that variable.

This reverts commit edccf32f7f36a8bc759b9482737e0c3efcb3a005.

This was reported to cause issues for as yet unknown reasons in
bug #78769. As this was intended as code cleanup, revert this from
7.4 at least. May reapply it to master later.

These were checking whether the instruction set is supported by
the host CPU, however they were only used to condition on whether
this instruction set is targeted at all. It would still use dynamic
dispatch (e.g. based on ifunc resolvers) to select the actual
implementation. Whether the target is guaranteed to support the
instruction set without dispatch is determined based on pre-defined
macros like __SSE2__.

This removes the configure-time builtin cpu checks to remove
confusion. Additionally this allows targeting an architecture that
is newer than the host architecture.

gcov builds can also be used with other tools like gcovr, so remove
the hard dependency on LTP.

This reverts commit db094b4b2e5ef0f0c30f412ce3a2516e31e17da7.

When building PHP outside of the source tree:

  mkdir custom-build-dir
  cd custom-build-dir
  ../path/to/php-src/configure

The directories need to be manually created including the pear directory
so the pear installation PHAR file doesn't need to be downloaded from
the remote location.

Closes GH-4639

This was once relevant for older versions of macs and autoconf 2.13.

Closes GH-4435

- Use Autoconf's default AC_CHECK_TYPES

Closes GH-4418