migrating to new backend format

[Havoc Pennington <hp redhat com>]

Hi,

If we use the patch to coalesce gconf XML files, then ~/.gconf will
become unreadable to GNOME 2.4 and earlier. That's not allowed.

So we can create ~/.gconf26 or something (better name?). Given this
there are these possible migration paths and maybe others:

 1. Have the gconf path contain ~/.gconf26 in front of ~/.gconf. 
    In principle, this means that the two will be merged. Unsetting 
    a setting should nuke the setting from both.

    Downsides: not well-tested, and creates a permanent efficiency 
    hit as operations will always check with both backends.
    Possible extreme weirdness if you log in to GNOME 2.4, change 
    things in ~/.gconf only, then back into 2.6 and suddenly 
    have both backends.

 2. Do a one-time migration (dump/load) from ~/.gconf into the 
    new ~/.gconf26 (probably the trigger to the migration is that 
    ~/.gconf exists and ~/.gconf26 doesn't).

 3. Screw it, you have to reconfigure gnome 2.6 from scratch.

Havoc