Linux 3.10: Replace create_proc_entry() with proc_create()

Add an afs_proc_create() compat function that uses the
appropriate kernel function based on a configure test.

Reviewed-on: http://gerrit.openafs.org/9854
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit 9b24013426e03a501fcaa6334ba5a9b48a8da3d1)

Change-Id: I976ef345b1638434026e852e577e1f4474171e3d
Reviewed-on: http://gerrit.openafs.org/9948
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>