runsv: update to match version 2.1.2 of runit

runsv: update to match version 2.1.2 of runit

Backport from upstream versions:
2.1.0
Thu, 24 Sep 2009 22:49:33 +0000
  * runsv.c: exit with error if [log/]supervise/control exists, but is
    not a fifo.
    [Code abstracted into a separate function to make it more compact
    for BusyBox.]

1.9.0
Mon, 05 May 2008 22:00:13 +0000
  * runsv.c: create temporary new status files for log/supervise/
    actually in log/supervise/.

1.7.2
Tue, 21 Nov 2006 15:13:47 +0000
  * runsv.c: really don't act on commands in state finish; minor.

function                                             old     new   delta
open_control                                           -     135    +135
update_status                                        553     612     +59
custom                                               223     242     +19
ctrl                                                 426     422      -4
warn_cannot                                           21      10     -11
runsv_main                                          1786    1662    -124
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 2/3 up/down: 213/-139)           Total: 74 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>