msxml3/tests: Execute ProcessingInstruction tests before other tests to avoid crashes under 64-bit Windows.

It seems that the ProcessingInstruction tests somehow trigger internal inconsistency
in 64-bit msxml under Windows, and I haven't found other ways to stop crashes on exit.
Signed-off-by: Dmitry Timoshkov <dmitry@baikal.ru>
Signed-off-by: Nikolay Sivov <nsivov@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>