Canonicalize all reply structures onto stack allocation and static
initialization, like already done in most other extension. So make
the code easier to understand and allow further simplifications by
subsequent commits. Also gaining a little bit efficiency by skipping
some heap allocations.
Dynamically sized buffers (where the upper bound isn't known), are
still allocated on heap.
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>