Re: missing documentation for streaming in-progress transactions

I didn't like this style because it is not descriptive enough. It is also not a

style adopted by Postgres. I suggest to add something like "This field was

introduced in version 2" or "This field is available since version 2" after the

field description.

+                Xid of the sub-transaction (will be same as xid of the transaction for top-level

+                transactions).

+</para>

Although, sub-transaction is also used in the documentation, I suggest to use

subtransaction. Maybe change the other sub-transaction occurrences too.