Review feedback: Use g_vfs_job_failed_literal.

Used in all appropriate locations.
Review feedback: Refactor device path derivation.

And fix reference leaks.
Review feedback: Minimise event check thread race during shutdown.

Theoretically, the event check could fire during unmount, resulting
in access to invalid backend state. We can try and minimise the
chance of this happening but can't elimiate it completely as the
LIBMTP_Read_Event call cannot occur with a lock or ref held as it
blocks and cannot be interrupted as part of the shutdown process.
If a lock was held, it would lead to a deadlock, and if a ref was
held, the backend would never finalize.

As it is, the race is now narrowed so that it's only applicable if
the unmount occurs at the point between where the MTP device is
looked up and when Read_Event is called.

And even before this change the race was incredibly rare as you'd
have to induce an MTP event in the middle of unmounting.

Finally, crashing while trying to terminate isn't the end of the
world.
Review feedback: Remove redundant lines.
Review Feedback: Correctly handle push/pull requests for directories.

Tomas explained the correct way to tell Nautilus to recurse directories
and issue individual copy operations for the contents, and it works!

Note that in the case of push, the contents don't copy correctly as
the push path is incorrect (uses filename instead of file id). I
can compensate for this, but that will be a separate change.
Review Feedback: AC_SUBST LIBMT_LIBS and LIBMTP_CFLAGS.

Whoops
Review Feedback: Add comment to all functions where mutex must be held.
Review Feedback: Use g_strv_length()
Review Feedback: Small cleanups.

* Use g_clear_object()
* Remove unnecessary code.
Review Feedback: Remove use of static buffer.

Use a dynamically allocated buffer instead to avoid any
multi-threading dangers.
Review Feedback: Fix warnings.
Review Feedback: use GHashTable more efficiently.
Review Feedback: Unconditional chain up finalize and dispose.
Review Feedback: Fix memory leaks and improve memory management.
Fix regression in thumbnail icon handling.

The preview icon and the main icon shouldn't get mixed up...
Fix hopelessly short timeout in file transfers.

The client code was using the default 25 second timeout for
file transfer operations, which is far too short.
Add display name support to gvfs-ls.
Ubuntu: Shared libgvfscommon