[MERGE-REQUEST] Always honor `--skip-present' in `replay'

Hi,

The patches listed below[*] fix `replay' so that `--skip-present' is
always honored.  Without these patches, it is not honored when `--new'
is passed along with `--skip-present', and it isn't honored when
`replay' is passed an exact revision (rather than a version).

  patch-18
      Honor `--skip-present' for exact revision replays.
  patch-19
      replay: Honor `--skip-present' when used along with `--new'.
  patch-20
      Added a unit-test for `replay'.

Patches 18 and 19 touch `whats-new.[ch]', `missing.[ch]', and
`cmd-replay.c'.  Patch 20 adds a file in the `tests' directory and
updates `tests/Makefile.in' accordingly.

Let me know if this looks acceptable.

Thanks,
Ludovic.


[*] Archive information:
    location:  http://www.laas.fr/~lcourtes/software/arch-2005/
    branch:    tla--devo--1.3