More fixes for 8.4 DTrace probes. Remove useless BUFFER_HIT/BUFFER_MISS

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

Commit: 471913a6a5d450fae4194ae626825fcc8e4604d6
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: 2009-03-23T01:52:38Z
Releases: 8.4.0
More fixes for 8.4 DTrace probes.  Remove useless BUFFER_HIT/BUFFER_MISS
probes --- the BUFFER_READ_DONE probe provides the same information and more
besides.  Expand the LOCK_WAIT_START/DONE probe arguments so that there's
actually some chance of telling what is being waited for.  Update and
clean up the documentation.

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