Linux 4.15: check for 2nd argument to pagevec_init

Linux 4.15: check for 2nd argument to pagevec_init

Linux 4.15 removes the distinction between "hot" and "cold" cache
pages, and pagevec_init() no longer takes a "cold" flag as the
second argument. Add a configure test and use it in osi_vnodeops.c .

Reviewed-on: https://gerrit.openafs.org/12824
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Marcio Brito Barbosa <mbarbosa@sinenomine.net>
Tested-by: Marcio Brito Barbosa <mbarbosa@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
(cherry picked from commit fb1f14d8ee963678a9caad0538256c99c159c2c4)

Change-Id: Ib9e0751e4900d984a4197d18ee9ebb1bdc7bf331
Reviewed-on: https://gerrit.openafs.org/12829
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>