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.

Change-Id: I4f3929849af032f2a483bc06bc5769f64085f1c4
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>