Use <stdint.h> and <inttypes.h> for c.h integers.

Use <stdint.h> and <inttypes.h> for c.h integers.

Redefine our exact width types with standard C99 types and macros,
including int64_t, INT64_MAX, INT64_C(), PRId64 etc.  We were already
using <stdint.h> types in a few places.

One complication is that Windows' <inttypes.h> uses format strings like
"%I64d", "%I32", "%I" for PRI*64, PRI*32, PTR*PTR, instead of mapping to
other standardized format strings like "%lld" etc as seen on other known
systems.  Teach our snprintf.c to understand them.

This removes a lot of configure clutter, and should also allow 64-bit
numbers and other standard types to be used in localized messages
without casting.

Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/ME3P282MB3166F9D1F71F787929C0C7E7B6312%40ME3P282MB3166.AUSP282.PROD.OUTLOOK.COM