Documentation window in monodevelop requires libgtkhtml3, and if it's missing, 
monodevelop crashes when trying to view documentation:

Unhandled Exception: System.DllNotFoundException: libgtkhtml-3.6.so.18
in (wrapper managed-to-native) Gtk.HTML:gtk_html_new ()
in <0x00060> Gtk.HTML:.ctor ()
in <0x00020> MonoDevelop.Gui.HelpViewer:.ctor ()
in <0x001d0> MonoDevelop.Gui.Pads.HelpTree:ShowDocs (System.String text, 
Monodoc.Node matched_node, System.String url)
in <0x0011b> MonoDevelop.Gui.Pads.HelpTree:RowActivated (System.Object o, 
System.EventArgs e)
in (wrapper delegate-invoke) System.MulticastDelegate:
invoke_void_object_EventArgs (object,System.EventArgs)
in <0x00096> GLib.Signal:voidObjectCallback (IntPtr handle, IntPtr gch)
in (wrapper native-to-managed) GLib.Signal:voidObjectCallback (intptr,intptr)
in <0x00000> <unknown method>
in (wrapper managed-to-native) Gtk.Application:gtk_main ()
in <0x00007> Gtk.Application:Run ()
in <0x0048a> MonoDevelop.Commands.StartWorkbenchCommand:Run ()
in <0x00a7e> MonoDevelop.SharpDevelopMain:Main (System.String[] args)