The vc-mistrust-permissions configuration variable is gone.

* vc/vc-cvs.el, vc/vc-hooks.el, vc/vc-rcs.el, vc/vc-sccs.el: Eliminate
vc-mistrust-permissions.  It was only relevant to the RCS and SCCS
back ends and defaulted to t. Code now always mistrusts permissions -
by actual measurement the effect on performance is negligible. As a
side effect bug#11490 is now irrelevant.