[parrot/parrot] 8e17e9: [core] #ifdef PARROT_SLOW_MOD or fast % mod

[GitHub]

  Branch: refs/heads/smoke-me/slow-mod
  Home:   https://github.com/parrot/parrot
  Commit: 8e17e9ee02cdf73cab7dcd71ef23ed36c6f4af23
      https://github.com/parrot/parrot/commit/8e17e9ee02cdf73cab7dcd71ef23ed36c6f4af23
  Author: Reini Urban <rurban at cpanel.net>
  Date:   2015-02-01 (Sun, 01 Feb 2015)

  Changed paths:
    M config/gen/config_h/feature_h.in
    M src/ops/core_ops.c
    M src/ops/math.ops
    M src/pmc/integer.pmc

  Log Message:
  -----------
  [core] #ifdef PARROT_SLOW_MOD or fast % mod

use optionally the 3.5% faster natural % for int mod,
which is "incorrect" or different with negative arguments.

mod is profiled as hot and slow (5.5%) in parrot-bench
with linux perf.