preferences: fix icon view -> canvas view leftover

This was lost in the massive renaming.
application: add an environment variable to debug no-app-menu scenarios

So that we can test under a stock environment the behavior when an app
menu is not provided by the shell (since we have fallback code for such
a case).

https://bugzilla.gnome.org/show_bug.cgi?id=681394
menus: make sure to show About and Help when no app menu is displayed

We had code for this, but it broke when we moved to a gear menu.

https://bugzilla.gnome.org/show_bug.cgi?id=681394
Fix other breakage from IconView->CanvasView renames

- fix loading of the desktop icon view
- don't use the term "Canvas" in translatable strings, since that's just
  an internal implementation detail

This also fixes
https://bugzilla.gnome.org/show_bug.cgi?id=681388
Updated Spanish translation
Updated Spanish translation
Improve error handling of directory loading
Make sure error dialog has a parent
Select first item in search results by default
release: prepare for 3.5.5
Updated Serbian translation
Updated Spanish translation
Update directory async test case
Add profiling support

Can now be profiled like so:
strace -ttt -f -o /tmp/logfile.strace nautilus
python plot-timeline.py -o prettygraph.png /tmp/logfile.strace

See: http://www.gnome.org/~federico/news-2006-03.html#09
Add a bunch of profiling points
Fix segfault when result list is empty

Commit 50711e28b introduced selecting the first result automatically,
but didn't handle the case where the result list is empty.

https://bugzilla.gnome.org/show_bug.cgi?id=681479
Add view options directly to the toolbar

Instead of having them buried in the menus.

https://bugzilla.gnome.org/show_bug.cgi?id=680985
Add a view menu button to the toolbar

https://bugzilla.gnome.org/show_bug.cgi?id=680985
Move bookmarks to app menu and only show add bookmark in page menu

https://bugzilla.gnome.org/show_bug.cgi?id=680985
Move enter location into the app menu

https://bugzilla.gnome.org/show_bug.cgi?id=680985