(vc-rcs-workfile-is-newer): New function.

(vc-rcs-workfile-is-newer): New function.
(vc-rcs-state-heuristic): Use it to guess the state of files with
non-strict locking.
(vc-rcs-find-most-recent-rev): Handle the case when a branch has been
set with -b, but not created yet.
(vc-rcs-fetch-master-state): With non-strict locking, compare file
contents in order to find the state.
(vc-rcs-checkin): Allow creation of branches with no changes.
(vc-rcs-unregister, vc-rcs-receive-file,
vc-rcs-set-non-strict-locking): New functions.