evaluate: Fix debug output

evaluate: Fix debug output

When introducing output_fp, debug output in src/evaluate.c was not
adjusted and therefore broke.

This patch restores eval debug output by applying the following changes:

- Change erec_print() and erec_print_list() to take a struct output_ctx
  pointer as first argument and use output_fp field as destination to
  print to.
- Drop octx_debug_dummy variable and instead use octx pointer from
  struct eval_ctx for debug output.
- Add missing calls to erec_destroy() in eval debug output which should
  eliminate another mem leak.

Fixes: 2535ba7006f22 ("src: get rid of printf")
Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>