- Select minimal vm image instead of generic ('C'), reducing size and boot time.
   - Windows needs 'C' image to not hang on booting
 - Update from Xenial to Bionic for linux tests.
   - ppc64 images don't have Bionic, set to Xenial
   - ppc64 is having misc failures with Xenial tools, so use GCC-9 and Clang-6
   - ppc64 cannot run MSAN
 - Add another test for more complete testing across architectures.
 - Enable fuzzers, msan and/or sanitizers most various tests.
 - Disable ASAN leak detection on aarch64, since it crashes under qemu
 - Reorder tests to be better grouped and running windows/macox tests lasts.
 - Enable verbose messages from sanitizers

CmakeLists.txt changes:
 - Enable warnings by default.
 - Add MAINTAINER setting to cmake
   - Enables extra warnings.
   - Enables fuzzers.
 - Add CI detection to cmake, currently auto-enables MAINTAINER mode.
 - Add detection of several more sanitizer features.
 - Test sanitizer features together, not just alone.
   This also helps with their inter-dependencies.

.gitignore changes:
 - Add switchlevels.