Log Message:
tex-tex4ebook{,-doc}: update to 0.3h

0.3h
- fixed issues with the validity and formatting of Epub 3 tables of contents
- fixed support for appendix chapters

0.3g
- the previous version introduced spurious "0" character in the
  metadata file, resulting in a validation error. This version fixes
  this issue.

0.3f
- fixed spurious numbers in Epub Table of Contents
- fixed support for \author command in Amsart class

0.3e
- TeX4ebook will use Calibre's `ebook-convert` command to create ebooks
  in Mobi and Azw formats if `kindlegen` is not available
- fixed cross-referencing error