This patch adds new builders that test against GCC 6 and Clang 3.8 respectivly.
They also enable both address and undefined sanitizer. MSAN currently won't work
since it requires a sanitized STL.
Google Benchmark's Travis build currently requires "sudo" to install newer
versions of CMake and similar. See this for more details:
https://docs.travis-ci.com/user/workers/container-based-infrastructure/
Since Google Benchmark was put into Travis before 2015-01-01, it gets the
standard infrastructure implicitly, so sudo works. But anyone who forks this
repository and tries to add Travis.CI (so they can see if the build works
before creating a PR) gets broken builds before this change.
This patch cleans up our use of generic macros and also merges changes in the
build system.
It adds options -DBENCHMARK_ENABLE_TESTING and -DBENCHMARK_ENABLE_SHARED.
