changes to cfengine-mode (was: prog-mode not available in earlier Emacsen, need help with cfengine.el)

[Ted Zlatanov]

I'd like to rename `cfengine-mode' to `cfengine2-mode', and
`cfengine-auto-mode' to `cfengine-mode' (`cfengine-auto-mode' loads
`cfengine3-mode' if it thinks a cfengine v.3 file is edited).

The effect on users of CFengine v.2 will be nil, since the detection is
very cautious and assumes v.2.  Users of v.3 will get `cfengine3-mode'.

Another approach is to rename `cfengine-mode' to `cfengine2-mode' and
`cfengine3-mode' to `cfengine-mode', effectively making v.2 support less
important.  **I like this approach better** because cfengine v.2 is
disappearing quickly, but it would break backwards compatibility so I
proposed it second.

Let me know what you think.  Thanks!

Ted