OTHER: rename 'lib' directory to 'backend_xmmsclient++'

I plan to replace the boost based c++ bindings with native Qt based bindings
in the long run
The currently there is libxmms2qt, but tru stated working on bindings based
on genipc

src/wscript

@@ -98,7 +98,7 @@ def build(bld):
     obj.target       = 'promoe'
     obj.includes     = incdirs
     obj.source       = sources
-    obj.uselib_local = 'promoe_lib'
+    obj.uselib_local = 'backend_lib'
     obj.add_objects  = 'promoe_data'
     obj.uselib       = 'QTCORE QTGUI AVAHI-CLIENT AVAHI-QT4'
     pass