implement split_escaped for interface file search
Address compiler warnings, revamp interface search

Removed g_interfaceDir variable, as it was unused.

Re-did the interface file search code to be less brittle. All non-Win32
platforms now try to use XDG_DATA_DIRS--to my knowledge XDG is used on
much more than just OS X.

ifdef'ed some macros to prevent compiler warnings.
use latest libbarobo