* xmlschemas.c include/libxml/schemasInternals.h
  include/libxml/xmlerror.h: Completion of the schema graph.
  Centralisation, more robustness of the schema document
  aquisition story. Centralised and restructured component fixup.
  Fixed attribute derivation when 'prohibiting' attribute uses.
  Added warnings: when schema documents cannot be localized
  during imports; when we get duplicate and pointless attribute
  prohibitions. Changed error reports for IDCs to report
  the relevant IDC designation as well (requested by GUY Fabrice).
  Misc code-cleanup.