* dbus/dbus-sysdeps.c (_dbus_file_get_contents): include filenames
in error messages
(_dbus_string_get_dirname): new
(_dbus_sysdeps_test): new
(_dbus_directory_open): include dirnames in error messages
* bus/config-parser.c: interpret <include> and <includedir> and
<servicedir> relative to config file location if the given
filename is not absolute.
* dbus/dbus-string.c (_dbus_string_find_byte_backward): new
