Always show two buttons in pathbar

The pathbar is pretty useless if there is only on button for the current directory.

This is a cherry-pick of 3cf2ca8ae26ca39534d26237dd25a756060617e0
from git@github.com:daschuer/nautilus.git
fixed scrolling with two buttons
Fix some compiler warnings
configure: Fixed source control detection for git
Fixed double definition of LOCALEDIR
pathbar: do not shink buttons below minimum
pathbar: display one button if two minumum buttons do not fit
Fix g_source_remove bug of NemoDesktopLinkMonitor

The function `g_source_remove' is used to remove GSource ids, not signal
handlers. To unlink handlers by id, `g_signal_handler_disconnect' has to
be used instead. However, handlers connected via
`g_signal_connect_object' get disconnected automatically if the object
that is supposed to be passed to the handler after signal emissions gets
destroyed. Unhooking the handlers in NemoDesktopLinkMonitor's finalize
function is therefore unnecessary.

Signed-off-by: Niklas Koep <niklas.koep@gmail.com>
Rename function `nemo_window_pane_close_slot'

The header for nemo-window-pane.h exposes the functions
`nemo_window_pane_close_slot' as well as `nemo_window_pane_slot_close'.
This naming is just unfortunate. To try and clarify the situation a bit,
rename `nemo_window_pane_close_slot' to
`nemo_window_pane_remove_slot_unsafe' as the latter really just removes
the slot from the GtkNotebook. The `*_unsafe' portion of the name refers
to the fact that it is not safe to call the function with the active
slot of a pane as this might crash Nemo.

Signed-off-by: Niklas Koep <niklas.koep@gmail.com>
Rename function `nemo_window_pane_slot_close' to..

`nemo_window_pane_close_slot'.

Signed-off-by: Niklas Koep <niklas.koep@gmail.com>
Switch to next tab after closing the active one

Closing the active tab would previously select the first inactive slot
in a pane. It is more common in other applications though to select
either the next slot (if one exists) or the previous one. Note that we
have to consult the GtkNotebook which holds the slots for this instead
of the pane's list of slots since the latter does not necessarily
represent the order in which slots are actually displayed in Nemo.

Signed-off-by: Niklas Koep <niklas.koep@gmail.com>
Fix warning when casting gpointer to gboolean

Signed-off-by: Niklas Koep <niklas.koep@gmail.com>
Revert bookmarks refactor (causes more issues than it fixes),

This reverts commit 6c890a95222228d3773fb6efe1f98f31f1102540.
Fix original unmount crash a different way
Show custom colors and emblems in places sidebar
bookmarks:  Use singleton for bookmark-list, track visited (for icon
updates), distinguish 'opened' network bookmarks from available.
bookmarks: ensure visited state for a newly-added bookmark
recent files: show/hide based on gtk remember-recent-files
setting.
places-sidebar:  Add dedicated bookmarks section.

New behavior:
- New user - xdg folders display under home/desktop, as before
- Upgrading user - all bookmarks are unchanged, still display in current position.
- Adding new bookmarks via menus - new items are placed under a Bookmarks category.
  They can be dragged to the My Computer section if desired.
- Performing any sort of drag operation (either a new drag from outside the sidebar
  or re-arranging bookmarks, will temporarily display the Bookmarks heading, to
  reveal the new section.  If the user ends the drag without dropping anything in this
  new section, the heading disappears again.
- Bookmarks can be dragged around between sections without restriction - the bookmark
  section will only show if there are items within it.
add the ability to show/hide all of the toolbar buttons