Fix comment typo
Prepare for a probable 10.10

We need room for the extra digit in the second part of the version.
Also add one for the third part too, just in case.
PU: wrapper: support? for 10.10

I know nothing about 10.10 (will it even be "10.10"?), but maybe the
"10.6 method" will continue to work there.

I will probably not use the next OS X during its beta period, so
I would appreciate it if someone could give me a clue as to whether
the code change in this commit is appropriate for the next release
(e.g. once any NDA has expired).

    Is the next release actually numbered 10.10?

        Does the output of the command "uname -r" say something like
        14.0?

    Does _vprocmgr_move_subset_to_user still exist?

        In 10.9, you could find it in liblaunch (used by libSystem):

            % nm /usr/lib/system/liblaunch.dylib | grep move_subset
            0000000000006739 T __vprocmgr_move_subset_to_user

    Does it still take (uid_t, const char*, uint64_t) args?

        This has historically only been documented in the
        opensource.apple.com release of launchd (liblaunch).
        Releases for new OS revs typically lag the actual OS release
        a bit (but usually not too much).

    Is it still effective?

        Does this command:

            echo foo|/usr/bin/pbcopy; ./test daemon=sys move-to-user=10.6 system=/usr/bin/pbpaste; sleep 1

        Have this output?:

            foo
            system(pbpaste) process exited 0

    Is it still needed?

        A bit more open-ended since there are more scenarios to test
        (e.g. ending a login session). The simplest would be
        something like this:

            echo foo|/usr/bin/pbcopy; ./test daemon=sys system=/usr/bin/pbpaste; sleep 1

        It is still necessary if you get this output:

            system(pbpaste) process exited 1