ctxcsn.c commit/rewind/graduate_commit_csn

[Howard Chu <hyc@symas.com>]

As I understand it, the pending_csn_list is maintained because we don't 
guarantee that operations commit in a particular order, and so op CSNs 
are in fact NOT sequential. This seems like a fundamental flaw.

Since CSNs are assigned early in the processing of an op, we really need 
a guarantee that write operations complete in the same order that 
they're received, or at least in the same order of their CSNs, otherwise 
CSNs are useless for actually describing the order in which to propagate 
changes.

--
 -- Howard Chu
 Chief Architect, Symas Corp.       Director, Highland Sun
 http://www.symas.com               http://highlandsun.com/hyc
 Symas: Premier OpenSource Development and Support