added a --relative (== -R) option. This is what Anthony Thyssen

suggested on the list recently. See the man page entry for details but
basically it changes the behaviour so that paths are not stripped,
thus allowing you to specify a single rsync command to sync lots of
directories/files while preserving the full path name of each file.
also fixed a bug in the handling of umasks when both the source and
destination machines are local. We need to reset the umask before the
exec to ensure that the child gets a correct umask.