pgsql: Assume that we have functional, 64-bit fseeko()/ftello().

Assume that we have functional, 64-bit fseeko()/ftello().

Windows has this, and so do all other live platforms according to the
buildfarm, so remove the configure probe and src/port/ substitution.

Keep the probe that detects whether _LARGEFILE_SOURCE has to be
defined to get that, though ... that seems to be still relevant in
some places.

This is part of a series of commits to get rid of no-longer-relevant
configure checks and dead src/port/ code.  I'm committing them separately
to make it easier to back out individual changes if they prove less
portable than I expect.

Discussion: https://postgr.es/m/15379.1582221614@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/799d22461a932aace890d61a82186e0d64de0ee8

Modified Files
--------------
configure                            | 30 ++-----------
configure.in                         | 13 ++----
src/bin/pg_dump/pg_backup_archiver.c |  9 ----
src/include/port.h                   | 13 +-----
src/include/port/win32_port.h        |  1 +
src/port/fseeko.c                    | 84 ------------------------------------
src/tools/msvc/Mkvcbuild.pm          |  2 +-
7 files changed, 11 insertions(+), 141 deletions(-)