cliopts (several minor changes. see description)

- use the Option::stmp member to store the backing char* for the default
  value:
  The whole reason stmp exists in the first place is so that the storage
  space for the default value is scoped with the actual options object, so
  use it for that.

- cliopts: Support --foo=bar style
  I don't know why I just realized I couldn't do this. but the fix is
  easy

- allow to hide options
  Some options are deprecated but should still be supported in case people
  rely on old behavior or forget to remember the new ones.

Change-Id: I6eda14f9d9ac7a3193e71127b514da2a59d48584
Reviewed-on: http://review.couchbase.org/38685
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>