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>
Fix broken link
Merge branch 'master' into pathbar_two_button

Conflicts:
	m4/gtk-doc.m4
	src/nemo-pathbar.c
Pathbar: make better use of Space in the two button shrinked state
Merge pull request #651 from nkoep/rework-tab-closing

Rework tab closing
Merge pull request #473 from daschuer/warning_fix

Warning fix
Merge pull request #466 from daschuer/pathbar_two_button

Pathbar two button
Merge pull request #732 from IanLee1521/doc-fix

Fix broken link
Merge pull request #652 from nkoep/fix-gpointer-to-gboolean-cast-warning

Fix warning when casting gpointer to gboolean