* include/libxml/parserInternals.h parser.c: had to change
  2 internal parsing API when processing document content
  to check the start and end of element content are defined
  in the same entity
* valid.c include/libxml/valid.h: attribute normalization can
  generate a validity error added xmlValidCtxtNormalizeAttributeValue()
  with the context to report it.
* SAX.c: fixed the last known bugs, crazy validation constraints
  when a document is standalone seems correctly handled. There
  is a couple of open issues left which need consideration especially
  PE93 on external unparsed entities and standalone status.
  Ran 1819 tests: 1817 suceeded, 2 failed and 0 generated an error in 8.26 s.
  The 2 tests left failing are actually in error. Cleanup done.
Daniel