MB-11305 Fix type used for sizeof() during {re,c}alloc

As identified by clang static analyser, use the correct type in
sizeof() {re,c}alloc.

Change-Id: I66cd8be2b8c1b0a7661294b6d799dfcdb190d269
Reviewed-on: http://review.couchbase.org/37838
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>