Rename I/O timing statistics columns to blk_read_time and blk_write_time.

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

Commit: 1dd89eadcd2648d7ca0baed3c7af16a04eb1aa26
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: 2012-04-29T22:13:33Z
Releases: 9.2.0
Rename I/O timing statistics columns to blk_read_time and blk_write_time.

This seems more consistent with the pre-existing choices for names of
other statistics columns.  Rename assorted internal identifiers to match.

Files