pgsql: Fix configure check for %z printf support after INT64_MODIFIER c

Fix configure check for %z printf support after INT64_MODIFIER changes.

The PGAC_FUNC_SNPRINTF_SIZE_T_SUPPORT test was broken by
ce486056ecd28050. Among others it made the UINT64_FORMAT macro to be
defined in c.h, instead of directly being defined by configure.

This lead to the replacement printf being used on all platforms for a
while. Which seems to work, because this was only used due to
different profiles ;)

Fix by relying on INT64_MODIFIER instead.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/7e3f728353fa9b36c7f98b6ec447d3f1b8deec14

Modified Files
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config/c-library.m4 |    3 ++-
configure           |    3 ++-
2 files changed, 4 insertions(+), 2 deletions(-)