pgsql: pg_upgrade: Check version of target cluster binaries

pg_upgrade: Check version of target cluster binaries

This expands the binary validation in pg_upgrade with a version
check per binary to ensure that the target cluster installation
only contains binaries from the target version.

In order to reduce duplication, validate_exec is exported from
port.h and the local copy in pg_upgrade is removed.

Author: Daniel Gustafsson <daniel(at)yesql(dot)se>
Discussion: https://www.postgresql.org/message-id/flat/9328(dot)1552952117(at)sss(dot)pgh(dot)pa(dot)us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/f06b1c598254f8adb2b7f51d6a7685618a7fb121

Modified Files
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src/bin/pg_upgrade/exec.c | 88 +++++++++++++++++++----------------------------
src/common/exec.c | 3 +-
src/include/port.h | 1 +
3 files changed, 38 insertions(+), 54 deletions(-)