[xml] Schema patch

[Kasimier Buchcik <kbuchcik 4commerce de>]

Hi,

the following main changes have been applied to the XML schema engine of 
libxml2:

1. Changed much of the error output. This has a low "nice" factor ;-)
   since a lot of the regression test results needed to be changed,
   but I am of hope that the gain of the error output will be more of
   importance to you. If this is fine with you, I will adapt the rest of
   the reports.
2. Activated namespace awareness during validation of the element
   content.
3. Added handling of xsd:any (this is not much tested yet).
4. Restructured and fixed parsing of <element>, <attribute> and
   <simpleType> to extract all required information + validation of its
   attributes and their values.
5. Changed xmlGetBooleanProp to additionally allow "0" and "1" for
   values of type boolean.
6. Completed parsing of xsd:annotation + its descendants xsd:appinfo and
   xsd:documentation (this was Bug 145247, submitted by Stefan Kost).
7. Added handling of substitution groups (this was Bug 145246, submitted
   by Stefan Kost).
8. Added handling of the facet "whiteSpace"; the engine tries now to
   correctly normalize attribute values and the character content of
   elements (this was Bug 104084, submitted by Sivaguru Sankaridurg).
9. Fixed a bug that occured when the derivation of attributes was
   checked (ComplexType, derivation by restriction). This bug was
   discovered by William Brack, running the regression tests on a 64bit
   machine.
10. Added namespace conversion if including XSDs with no target
   namespace.

Greetings,

Kasimier