Fix XML regression tests failure

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