Consolidate deprecated API implementations into a single 'legacy.c' file

I've been getting questions from folks about various confusions with
these older files. This should help lay away some of the confusion :)

Change-Id: I75e36b5ce9ed18575eb49ef05c91bbf2f0e2c330
Reviewed-on: http://review.couchbase.org/43716
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>