Add NetBSD support in asan_symbolize.py

Summary:
Part of the code inspired by the original work on libsanitizer in GCC 5.4 by Christos Zoulas.

Sponsored by <The NetBSD Foundation>

Reviewers: joerg, filcab, vitalybuka, kcc, fjricci

Reviewed By: fjricci

Subscribers: kubamracek, llvm-commits, #sanitizers

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D36484

llvm-svn: 310413