patches for items from TODO list

Hello all,

We would like to contribute to the Postgresql community by implementing
the following items from the TODO list
(http://developer.postgresql.org/todo.php):
. Allow COPY to understand \x as a hex byte . Allow COPY to optionally
include column headings in the first line . Add XML output to COPY

The changes are straightforward and include implementation of the
features as well as modification of the regression tests and documentation.

Before sending a diff file with the changes, we would like to know if
these features have been already implemented.

Best regards,
Jason Lucas and Sergey Ten
SourceLabs

Dependable Open Source Systems