- specfile: added rcs.keyring as source

- rcs 5.9.4:
+ documentation improvements

- rcs 5.9.3:
- compatibility w/ RCS 2.x file format dropped
- fix crash on co/ci without changes on a branch
- includes changes from 5.9.2:
- avoid possibly failing command in backticks
- handle low-memory situations like RCS 5.7 (mostly)
- default for env var ‘RCS_MEM_LIMIT’ relaxed
- includes changes from 5.9.1:
- avoid ‘grep -q’
- ‘PROGRAM --help’ shows home page / "gethelp" info
- includes changes from 5.9.0:
- common option ‘-V’ obsoleted by ‘--version’
- ‘rcsmerge --help’ mentions ‘-A’, ‘-E’, ‘-e’
- ‘ident -VN’ and ‘merge -VN’ now signal error
- ident(1) recognizes Subversion "fixed-width keyword syntax"
- new co(1) option ‘-S’ for "self-same" mode
- several RCS commands "internalized" into rcs(1)
- ‘--help’ output includes a one-line description
- effects of ‘-VN’ (N ∈ {3,4,5}) documented
- includes changes from 5.8.2:
- fix wrong symbolic name dereference
- ‘integrity’ value syntax better specified
- New manual chapter: RCS file format
- Manpages refer to info documentation
- Script to trim "junk at end of file" posted