Consider AppStream version as a string

[tintou]

Always store the AppStream metadata version as a string and compare it like any other version. This allows to have 0.10 > 0.8 for instance.

[hughsie]

Don't you need to add the new symbols to appstream-glib.map?

[tintou]

It looks like adding it to appstream-glib.map isn't necessary:

{
global:
    as_*;
local:
    *;
};

[hughsie]

as_*;