gvfs changes

[Alexander Larsson <alexl redhat com>]

Kinda late, but here is the gvfs changes I did yesterday as per the
announce freeze thing:

First of all there was some issues with the statically linked code in
common/ that registered types twice with the same name when backends
used the gvfs module. Worked around this with a get_type hack.

There was a major restructuring of the locking in the volume monitor so
that it avoids deadlocks and is actually threadsafe. This change also
had some fallout bugs that were fixed.

Fixed a NULL dereference in computer:// when mounting a drive with no
volumes.

I made the gvfs mount icons use fallbacks so that the icon for audio cds
(cdda:) works.

Fixed another NULL crash when host == NULL in the uri parsing code.

Disabled leftover debug logging from fuse daemon.

Fixed one case where we didn't use that gvfs standard timeout. This hit
us e.g. when automounting network://.