[Android] Add a contrib patch for libxml and activate it in the build

[Rémi Duraffort]

> What do we need XML for?
>  - Styled subtitles (somehow important)
>  - DASH (important for mobile)
>  - XSPF, ITML and other playlist formats (somehow important)
>  - lua, subsusf and rss (not really important)
lua is important for website parsing scripts (youtube, icecast, ...)



> VLC xml API seems to be SAX based (confirmation?) and not DOM-based,
> which makes a bit of sense, I think.
Yes SAX sounds better on embedded devices.


> libXML is huge and booring.
> We should look at alternative, like expat (small but slow) or
> rapidxml/tinyxml. However, I think rapidxml and tinyxml do not have a
> SAX api, but only a DOM one.
> ANd then do a LGPL module on it.
libexpat is the only one (among the three you mentionned) to support
SAX, so it should be the default choice. Moreover, libexpat is still
maintained (last release from march 2012).


My 2 cents.

-- 
Rémi Duraffort | ivoire
http://ivoire.dinauz.org/blog/