DISPATCH-1467: enable AddressSanitizer build option (ASAN)

To run the AddressSanitizer, define RUNTIME_CHECK=asan via CMake:

  cmake .. -DRUNTIME_CHECK=asan

This patch updates the .travis.yml file to enable address and
undefined behavior checking.  Also included are minor code tweaks to
issues found when running with the sanitizer enabled.

This closes #608
9 files changed