Proposed commit log message:
```
Mk/bsd.options.desc.mk: Add version control OPTIONS descriptions
- Add CVS description
- Add DARCS description
- Add GIT description
- Add MERCURIAL description
- Add PERFORCE description
- Rename SVN to SUBVERSION
devel/anjuta: rename OPTION SVN to SUBVERSION
devel/git: rename OPTION P4 to PERFORCE, SVN to SUBVERSION
devel/ocaml-opam: rename OPTION HG to MERCURIAL
devel/thunar-vcs-plugin: rename OPTION SVN to SUBVERSION
devel/viewvc-devel: rename OPTION SVN to SUBVERSION
devel/viewvc: rename OPTION SVN to SUBVERSION
net-mgmt/observium: rename OPTION SVN to SUBVERSION
net-mgmt/rancid3: rename OPTION SVN to SUBVERSION
ports-mgmt/portshaker: rename OPTION SVN to SUBVERSION, HG to MERCURIAL
security/hydra: rename OPTION SVN to SUBVERSION
security/medusa: rename OPTION SVN to SUBVERSION
shells/scponly: rename OPTION SVN to SUBVERSION, typo fix in SVNSERVE_DESC
www/trac-devel: rename OPTION SVN to SUBVERSION
Reviewed_by: koobs, adamw
Approved by: koobs (ports, mentor)
Differential_Revision: D17459
MFH: No (OPTION description updates)
```