Added support for the opensrf XID, which is a transaction string that's passed

Added support for the opensrf XID, which is a transaction string that's passed
around via the jabber message and inserted into each logged message to relate
activity accross different processes

implemented a child onExit handler for the C stack for cleaning up db connections, etc.

git-svn-id: svn://svn.open-ils.org/OpenSRF/trunk@814 9efc2488-bf62-4759-914b-345cdb29e865