Log Message:
-----------
Add SXid() and Transact() module functions.
Transact, with fair safety, assumes that it will be invoked within a
transaction.
SXid gets the current SubTransactionId as an XID instance.
Modified Files:
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be/src:
module.c (r1.20 -> r1.21)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/be/src/module.c.diff?r1=1.20&r2=1.21)