The virCaps structure gathered a ton of irrelevant data over time that.
The original reason is that it was propagated to the XML parser
functions.

This patch aims to create a new data structure virDomainXMLConf that
will contain immutable data that are used by the XML parser. This will
allow two things we need:

1) Get rid of the stuff from virCaps

2) Allow us to add callbacks to check and add driver specific stuff
after domain XML is parsed.

This first attempt removes pointers to private data allocation functions
to this new structure and update all callers and function that require
them.

by running this command:
git ls-files -z | xargs -0 perl -pi -0777 -e 's/\n\n+$/\n/'
This is in preparation for a more strict make syntax-check
rule that will detect trailing blank lines.