Refactoring: give split_point_c its own class
Refactoring: move parse_arg_split_parts() to common library

Goal: mmg should be able to use it for split arg validation.
Refactoring: use fourcc_c class in FLV reader
FLV reader: fix VP6 reading

Fixes #836.
Translations: update Spanish
Translations: update list of translatables
Man page translations: update Dutch
Man page translations: update list of translatables
Ignore generated HTML files
Output builder name (saxon-he), not interpreter (java)