pgsql: Require stdint.h

Require stdint.h

stdint.h belongs to the compiler (as opposed to inttypes.h), so by
requiring a C99 compiler we can also require stdint.h
unconditionally. Remove configure checks and other workarounds for
it.

This also removes a few steps in the required portability adjustments
to the imported time zone code, which can be applied on the next
import.

When using GCC on a platform that is otherwise pre-C99, this will now
require at least GCC 4.5, which is the first release that supplied a
standard-conforming stdint.h if the native platform didn't have it.

Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Discussion: https://www.postgresql.org/message-id/flat/5d398bbb-262a-5fed-d839-d0e5cff3c0d7%402ndquadrant.com

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/957338418b69e9774ccc1bab59f765a62f0aa6f9

Modified Files
--------------
configure | 73 ----------------------------------------------
configure.in | 2 --
src/include/c.h | 15 ++--------
src/include/pg_config.h.in | 14 ---------
src/timezone/README | 14 ++-------
src/tools/msvc/Solution.pm | 6 +---
6 files changed, 5 insertions(+), 119 deletions(-)