Log Message:
Changes 0.0.2:
- Better handling of invalid input in RVNGDirectoryStream functions.
- Add documentation for RVNGDirectoryStream.
- Add text:outline-level to allowed paragraph properties. This is to allow
  import libraries to handle headings properly.
- Properly handle units in all generators, instead of expecting everything is
  in inches.
- Implement open/closeGroup for RVNGSVGDrawingGenerator.
- Improve handling of layers in RVNGSVGPresentationGenerator.
- Handle master pages in RVNGSVGDrawingGenerator and
  RVNGSVGPresentationGenerator.
- Simple handling of tables in RVNGSVGDrawingGenerator and
  RVNGSVGPresentationGenerator: just create a text box for each cell.
- Fix return value of RVNGStringStream::seek when seeking to end.
- Fix some warnings found by Coverity.
- Use symbol visibility on Linux. The library only exports public functions
  now.
- Fix several crashes or hangs when reading broken OLE2 or Zip files, found
  with the help of american-fuzzy-lop.
- Add fo:language, fo:country and fo:script to allowed span properties.
- Handle headings in RVNGHTMLTextGenerator.