Fix assorted confusion between Oid and int32.

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

Commit: 390ed56eb7fb8cc4ba2a7cd6360b41883601908e
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: 2014-12-11T20:41:20Z
Releases: 9.4.0
Fix assorted confusion between Oid and int32.

In passing, also make some debugging elog's in pgstat.c a bit more
consistently worded.

Back-patch as far as applicable (9.3 or 9.4; none of these mistakes are
really old).

Mark Dilger identified and patched the type violations; the message
rewordings are mine.

Files