Make the use of madvise() with MADV_DONTDUMP configurable

We have run into problems with ATS 5.3.x when using madvise() with the MADV_DONTDUMP option to exclude IO buffers from core files. Under load, we have seen high cpu loads and very slow time to serve times when allocating IO buffers and marking them with this flag. We have had to disable calls to madvise() in ats_madvise(), rebuild and redeploy to fix this problem. We'd like to make the use of madvise() with the MADV_DONTDUMP option configurable. The PR associated with this ticket uses a patch from TS-3417 that implements making MADV_DONTDUMP configurable.