A new version of libXML changes the output format, this patch
adapts the new "expected" file introduced in
PostgreSQL commit 085423e3.
Slight modifications by me.

This patch will not fail the current Pulse run in any way, because
the Pulse systems do not yet use the new libXML library, and therefore
are happy with xml.out and xml_1.out. I stripped down the regression
tests and this is the output without the patch:

parallel group (14 tests):  limit prepare conversion xml rowtypes copy2 polymorphism sequence without_oid temp truncate domain rangefuncs alter_table
     limit                ... ok (0,24 sec)  (diff:0,07 sec)
     copy2                ... ok (2,44 sec)  (diff:0,07 sec)
     temp                 ... ok (3,83 sec)  (diff:0,07 sec)
     domain               ... ok (7,12 sec)  (diff:0,10 sec)
     rangefuncs           ... ok (12,15 sec)  (diff:0,09 sec)
     prepare              ... ok (0,49 sec)  (diff:0,06 sec)
     without_oid          ... ok (3,49 sec)  (diff:0,07 sec)
     conversion           ... ok (1,19 sec)  (diff:0,17 sec)
     truncate             ... ok (4,03 sec)  (diff:0,06 sec)
     alter_table          ... ok (27,88 sec)  (diff:0,32 sec)
     sequence             ... ok (3,18 sec)  (diff:0,08 sec)
     polymorphism         ... ok (3,13 sec)  (diff:0,11 sec)
     rowtypes             ... ok (2,17 sec)  (diff:0,09 sec)
     xml                  ... FAILED (1,69 sec)  (diff:0,39 sec)
test variadic_parameters  ... ok (1,57 sec)  (diff:0,07 sec)
test default_parameters   ... ok (0,68 sec)  (diff:0,07 sec)

=======================
 1 of 97 tests failed.
=======================

This is the output with the patch:

parallel group (14 tests):  limit prepare conversion xml rowtypes copy2 polymorphism sequence without_oid temp truncate domain rangefuncs alter_table
     limit                ... ok (0,21 sec)  (diff:0,10 sec)
     copy2                ... ok (1,95 sec)  (diff:0,06 sec)
     temp                 ... ok (3,41 sec)  (diff:0,26 sec)
     domain               ... ok (6,67 sec)  (diff:0,19 sec)
     rangefuncs           ... ok (11,55 sec)  (diff:0,09 sec)
     prepare              ... ok (0,41 sec)  (diff:0,06 sec)
     without_oid          ... ok (2,91 sec)  (diff:0,06 sec)
     conversion           ... ok (0,96 sec)  (diff:0,15 sec)
     truncate             ... ok (3,62 sec)  (diff:0,09 sec)
     alter_table          ... ok (25,79 sec)  (diff:0,22 sec)
     sequence             ... ok (2,89 sec)  (diff:0,06 sec)
     polymorphism         ... ok (2,50 sec)  (diff:0,09 sec)
     rowtypes             ... ok (1,87 sec)  (diff:0,12 sec)
     xml                  ... ok (1,54 sec)  (diff:0,30 sec)
test variadic_parameters  ... ok (1,43 sec)  (diff:0,07 sec)
test default_parameters   ... ok (0,43 sec)  (diff:0,07 sec)

======================
 All 97 tests passed.
======================

Fix #550

The order the rows were being aggregated was not well-defined, even though
I tried to add ORDER BYs to the queries. Putting the ORDER BY inside the
aggregate does the trick.

platform-specific result ordering.  Per buildfarm results.

observe the xmloption.

Reorganize the representation of the XML option in the parse tree and the
API to make it easier to manage and understand.

Add regression tests for parsing back XML expressions.

- Add new SQL command SET XML OPTION (also available via regular GUC) to
  control the DOCUMENT vs. CONTENT option in implicit parsing and
  serialization operations.

- Subtle corrections in the handling of the standalone property in
  xmlroot().

- Allow xmlroot() to work on content fragments.

- Subtle corrections in the handling of the version property in
  xmlconcat().

- Code refactoring for producing XML declarations.

libxml as the detail message.

As per <http://archives.postgresql.org/pgsql-hackers/2006-12/msg01087.php>.

For converting error codes to messages, we only need to cover those codes
that we raise ourselves now.

function xmlagg.

with new GUC parameter "xmlbinary" that controls the output encoding, as
per SQL/XML standard.

declarations are ignored and removed, in binary mode they are honored as
specified by the XML standard.

coercion to type xml was a mistake.  Escape values so they are valid
XML character data.

- correct error codes
- do syntax checks in correct order
- strip leading spaces of argument

sets the items, and serializes the value back (rather than adding an
arbitrary number of XML preambles as before).

The libxml memory management via palloc had to be disabled because it
crashes when libxml tries to access memory that was helpfully freed
earlier by PostgreSQL.  This needs further thought.