Fix potential memory leak in _fm_folder_event_file_added().

It returns TRUE if duplicate adding was called for the same file so
extra reference leaves and file will stick indefinitely.
Fix memory corruption in _lookup_in_children() due to wrong cycle iteration.
Fix regression bug (support for obex://[xx:xx:xx:xx:xx:xx]/ URIs)
Remove disabled code (inside #if 0 ... #endif) in fm_path_new_for_display_name().