Print distribution information like distribution type, distribution column (if
any) and Datanodes where a relation is distributed in \d+ output from psql.
Merge branch 'master' of ssh://postgres-xc.git.sourceforge.net/gitroot/postgres-xc/postgres-xc
Param handling re-work (Fix for bug ID: 3522907)

Moved the parameter handling part from the plan phase to the
execute phase. See bug ID 3522907 for details.
Ship OUTER JOINs to datanodes in following cases
1. An equi-outer-join between the distribution columns of two distributed tables
such that the tables are distributed on same set of nodes and distribution
strategy is same and datatype of distribution column is same, is shippable to
the datanodes where the distributed tables are distributed.
2. An outer-join between a distributed and a replicated relation is
shippable to the datanodes where distributed relation is distributed if the
replicated relation is replicated on those nodes and the outer side of join is
distributed relation.
3. An outer-join between two replicated relations shippable to a datanode where
both the relations are available.

Justification for shippability can be found in mail thread with subject
"shipping outer joins" on pgxc-hackers mailing list.