Обсуждение: pgsql: Update config/ax_pthread.m4 to latest upstream version.

Update config/ax_pthread.m4 to latest upstream version.

This change doesn't fix any bugs that we've heard about, but it seems
like a good idea on general principles to track upstream occasionally.

Discussion: https://postgr.es/m/3320.1542647565@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/df303aff6601a893cf83c26ffd6c7eb5fb6b067e

Modified Files
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config/ax_pthread.m4 | 311 +++++++++++++++++++++++++-------------
configure            | 411 ++++++++++++++++++++++++++++++++++++++-------------
2 files changed, 516 insertions(+), 206 deletions(-)