Fix overflow check in tm2timestamp (this time for sure).

Tom Lane <tgl@sss.pgh.pa.us>

Commit: cf678140548b0f0fdef36f314bb84e07e15b8c16
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: 2013-03-04T20:14:28Z
Releases: 8.4.17
Fix overflow check in tm2timestamp (this time for sure).

I fixed this code back in commit 841b4a2d5, but didn't think carefully
enough about the behavior near zero, which meant it improperly rejected
1999-12-31 24:00:00.  Per report from Magnus Hagander.

Files