pgsql: Make configure check for IPC::Run when --enable-tap-tests is spe

Make configure check for IPC::Run when --enable-tap-tests is specified.

The TAP tests mostly don't work without IPC::Run, and the reason for
the failure is not immediately obvious from the error messages you get.
So teach configure to reject --enable-tap-tests unless IPC::Run exists.
Mostly this just involves adding ax_prog_perl_modules.m4 from the GNU
autoconf archives.

This was discussed last year, but we held off on the theory that we might
be switching to CMake soon. That's evidently not happening for v10,
so let's absorb this now.

Eugene Kazakov and Michael Paquier

Discussion: https://postgr.es/m/56BDDC20.9020506@postgrespro.ru
Discussion: https://postgr.es/m/CAB7nPqRVKG_CR4Dy_AMfE6DXcr6F7ygy2goa2atJU4XkerDRUg@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/c254970ad6092d201443cced570450d5b29d4234

Modified Files
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aclocal.m4 | 1 +
config/ax_prog_perl_modules.m4 | 77 +++++++++++++++++++++++++++++++++++++++++
configure | 78 ++++++++++++++++++++++++++++++++++++++++++
configure.in | 3 ++
4 files changed, 159 insertions(+)