MFC r199895:

MFC r199895:
  Change memory managment from a fixed size array to a list.
  This is needed to avoid running into out of buffer situations
  where we cannot alloc a new buffer because we hit the array size
  limit (ZBUF).
  Use a combined allocation for the struct and the actual data buffer
  to not increase the number of malloc calls. [1]

  Defer initialization of zbuf until we actually need it.

  Make sure the output buffer will be large enough in all cases.

  Details discussed with: kib [1]
  Reviewed by:            kib [1]

git-svn-id: svn://svn.freebsd.org/base/stable/8@200140 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f