[xml] streaming XML Schema

[Kasimier Buchcik <kbuchcik 4commerce de>]

Hi,

the XML Schema processor has been changed to be able to work
in streaming mode. No public API has been added yet to use
it on streams - but should be available soon. We intend to support
SAX2- and XMLReader-driven validation.

The XS test suite has been updated to work on the latest tests
available from W3C.

The current status of the tests:

## Running XML Schema tests (NIST)
Ran 23170 of 23170 tests (3953 schemata): 69 failed ( 2 internal )

## Running Schema tests (Sun)
Ran 193 of 193 tests (40 schemata): 40 failed ( 9 unimplemented 14
 skip-invalid-schema )

## Running Schema tests (Microsoft)
Ran 7230 of 7230 tests (4686 schemata): 607 failed ( 50 unimplemented 50
skip-invalid-schema ) 4 leaks

The chang to the code is significant, so I hope you'll switch
to use this version and provide feedback if some new/old bugs sneaked
in.

Greetings,

Kasimier