RELAX NG schemas for OOXML, from the published ECMA-376 standard.

The two archives are the standard as Ecma International publishes it:
part 4 (Transitional Migration Features, 5th edition, December 2016)
and part 2 (Open Packaging Conventions, 5th edition, December 2021).
Each archive holds the specification text and two electronic annexes;
the RELAX NG annex is the one unpacked here. The cofficeotron document
validator reads the schemas at run time.

The schemas are downloaded rather than kept in the source tree because
Ecma International publishes them under its own copyright terms, not
under an open source license.

Two patches relax the transitional markup schemas the same way the
Java officeotron 0.8.8 release patched its schema copies, to accept
constructs that documents in the wild contain:

- spreadsheet-text-xml-space.patch: spreadsheet text elements accept
  the xml:space attribute.
- bullet-size-percent-mille.patch: bullet sizes accept the
  percent-mille integers that the first edition of ECMA-376 defined.