data type serialization module

This merge request introduce a module to serialize and de-serialize vlc data types.
It is part of a series of merge requests, which aim to delegate preparse tasks to a dedicated preparse process, mainly for the medialibrary and vlc playqueue use cases.

The preparse process integration will be splitted in four merge requests

1. introduce module of serialization/deserialization
2. preparse process basis
3. implementation of vlc_spawn() for win32 (merged)
4. integrate use of preparse process in the medialibrary module and vlc playqueue.

When vlc preparse resources, it generate and set input_item_t which imply es_format_t in association with the ressource.
The protocol of communication between vlc process and the preparse process (see MR preparse basis for the protocol details),
require to serialize resulting objects of the preparse on the preparse process side. On the vlc side those objects needs to be deserialized.