Pull up following revision(s) (requested by hannken in ticket #771):

sys/kern/subr_pserialize.c: revision 1.11

Function pserialize_perform() usually succeeds after two cross calls
so defer kpause() to iterations three and above.

Speeds up VOP_REVOKE() on /proc/XXX/status by a factor of ~12.

Ok: core@

(martin)