Might as well check include timestamps and cache the include file
CamelCase uses for the non-git case too.

The camelcase cache file is now named:

  for git:      .checkpatch-camelcase.git.<commit_id>
  for non-git:  .checkpatch-camelcase.date.<YYYYMMDDhhmm>

All .checkpatch-camelcase* files are deleted if not current.
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>