This patch implements use_madv_dontdump flag suggested in https://code.google.com/p/address-sanitizer/issues/detail?id=345 . The flag disables dumping of shadow memory to corefile (which takes hours on 64-bit platforms). Tested on Linux x64.
I didn't add a testcase - generating a predictable corefile is hard given the zoo of modern crash reporters. E.g. see https://bugs.launchpad.net/ubuntu/+source/apport/+bug/1346497 (Apport from stock Ubuntu 14 multiples core limit by 1000).