Replace emallocz with ecalloc.

Signed-off-by: Christoph Lohmann <20h@r-36.net>
Clear urgency hint on sel == c

 - Run "tabbed xterm -into".
 - Open a new tab using Ctrl+Shift+Enter, switch to it using Ctrl+Tab.
 - Run "sleep 2; printf '\a'".
 - Quickly change back to the first tab (c = 0) and wait for the second
   one (c = 1) to get the urgency hint.
 - Close the first tab using Ctrl+Q or Ctrl+D. This sets sel = 0 and c =
   0, so focus() won't touch the urgency hint.
 - Now, the urgency hint on the second tab has not been cleared. Open a
   new tab to verify it.

Signed-off-by: Christoph Lohmann <20h@r-36.net>
tabbed: UnmapNotify patch

Hi,

Simple patch for tabbed that prevents tabbed from killing a client that it
should no longer be managing due to an UnmapNotify event.

Add support for UnmapNotify; allows a window to map and unmap without
needing it to be destroyed.

Thanks,
Okan

Signed-off-by: Christoph Lohmann <20h@r-36.net>
movetab(): Move selected tab instead of switching

Before this patch, movetab() just switched positions of the selected tab with
the new position. This resulted in unexpected behaviour when „moving“ a tab over
one end of the list.

Now tabs are moved correctly by the specified amount of indizes.

Signed-off-by: Christoph Lohmann <20h@r-36.net>