pgsql: Fix namespace handling in xpath function

Fix namespace handling in xpath function

Previously, the xml value resulting from an xpath query would not have
namespace declarations if the namespace declarations were attached to
an ancestor element in the input xml value.  That means the output value
was not correct XML.  Fix that by running the result value through
xmlCopyNode(), which produces the correct namespace declarations.

Author: Ali Akbar <the.apaan@gmail.com>

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/79af9a1d2668c9edc8171f03c39e7fed571eeb98

Modified Files
--------------
src/backend/utils/adt/xml.c         |   34 ++++++++++++++++++++++++++--------
src/test/regress/expected/xml.out   |   15 +++++++++++++++
src/test/regress/expected/xml_1.out |   12 ++++++++++++
src/test/regress/sql/xml.sql        |    2 ++
4 files changed, 55 insertions(+), 8 deletions(-)