pgsql: libpq: Deprecate pg_int64.

libpq: Deprecate pg_int64.

Previously we used pg_int64 in three function prototypes in libpq. It
was added by commit 461ef73f to expose the platform-dependent type used
for int64 in the C89 era. As of commit 962da900 it is defined as
standard int64_t, and the dust seems to have settled.

Let's just use int64_t directly in these three client-facing functions
instead of (yet) another name. We've required C99 and thus <stdint.h>
since PostgreSQL 12, C89 and C++98 compilers are long gone, and client
applications very likely use standard types for their own 64-bit needs.
This also cleans up the obscure placement of a new #include <stdint.h>
directive in postgres_ext.h, required for the new definition. The
typedef was hiding in there for historical reasons, but it doesn't fit
postgres_ext.h's own description of its purpose and there is no evidence
of client applications including postgres_ext.h directly to see it.

Keep a typedef marked deprecated for backward compatibility, but move it
into libpq-fe.h where it was used.

Reviewed-by: Peter Eisentraut <peter(at)eisentraut(dot)org>
Discussion: https://postgr.es/m/CA%2BhUKGKn_EkNNGMY5RzMcKP%2Ba6urT4JF%3DCPhw_zHtQwjvX6P2g%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3c86223c998280ea313480d319ec39f802453218

Modified Files
--------------
doc/src/sgml/libpq.sgml | 2 +-
doc/src/sgml/lobj.sgml | 6 +++---
src/include/postgres_ext.h | 5 -----
src/interfaces/libpq/fe-lobj.c | 30 +++++++++++++++---------------
src/interfaces/libpq/libpq-fe.h | 12 ++++++++----
src/test/examples/testlo64.c | 7 ++++---
6 files changed, 31 insertions(+), 31 deletions(-)