Fix unchecked errors on get_rel_size
Fix invalid mixing of pointer, oid and int lists.
Change xact_callback behavior.

Previously, one xact_callback was registered for every modified relation.
Now, only one is registered, and a list of modified relations is kept in memory.
Re-implement GetUserMapping, so as not to care about nested errors management.
Style according to pg_indent.
Fix conversions from integers "0" to NULL. Fix #45.
Add regression tests for "where id = 0" predicate.
Sqlalchemy: Fetch all columns if no columns are specified. (Fix #42)
Fix warning with python3
Add missing safeguard for 9.2
Allows unknown types to be used in quals.
Added support for savepoints.
Call commit/rollback even for unmodified foreign tables.
Fixed typo in the testfdw class.
Updated the Python 3.3 tests to reflect the new transaction hooks.
Updated the Python 2.7 tests to reflect the new transaction hooks.
The sub_commit/sub_rollback routines should be called only at the current depth.
Added tests for the savepoints hooks.
Some test cleanup.
Pgindent