rm_desc patch

This patch basically does two things: (1) call rm_desc() after redo error;
(2) change ABC_desc() to use StringInfo. A thinko in gist_desc() is also
fixed.

Per discussion with Tom,

Regards,
Qingqing

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Sample output:
[qqzhou(at)amd64 pginstall]$ postmaster -Ddata
LOG: database system was interrupted while in recovery at 2006-03-22
17:24:04 CST
HINT: This probably means that some data is corrupted and you will have
to use the last backup for recovery.
LOG: checkpoint record is at 0/C784350
LOG: redo record is at 0/C784350; undo record is at 0/0; shutdown TRUE
LOG: next transaction ID: 973; next OID: 32798
LOG: next MultiXactId: 1; next MultiXactOffset: 0
LOG: database system was not properly shut down; automatic recovery in
progress
LOG: redo starts at 0/C7843A0
PANIC: -- some redo complain --
CONTEXT: redo insert: rel 1663/16384/16418; tid 872/1
LOG: startup process (PID 3213) was terminated by signal 6
LOG: aborting startup due to startup process failure