[virt-tools-list] [libosinfo] add datamap support

[Christophe Fergeau]

This patch series adds datamap support to libosinfo. This is a way for
installers to automatically map generic string values used in libosinfo
public API to OS-specific string values. For example, one can map
a generic 'fr_FR' value for keyboard to a linux keymap, or things
like that.

The way it's done is by defining various <datamap> nodes in
XML files, and by adding a 'value-map' attribute referencing the
appropriate datamap to /install-script/config/param nodes.

I'm also planning to use datamaps to map Windows ISO labels to generic
language codes.

Christophe