Travis: Enable additional sanitizer tests - Re-purpose the non-SIMD test to test with MSan as well. - Re-purpose the ASan test to test with UBSan as well. - Use the default Travis build environment rather than specifying Ubuntu 14.04. I think I added 'dist: trusty' back when 14.04 was newer than the default, but now it's older than the default. - Enable verbose output for any unit tests that fail (so we can see the sanitizer output.)