Add --cc-abi-flags option to configure.py
Use -Werror only when --maintainer-mode is set as warnings will sneak
in on platforms/configs I don't test regularly, and that shouldn't
break end-user builds.
Make it possible to remove Boost dependency by disabling a few modules
(though including X.509 and TLS).
Add cpuid support for new x86 feature flags like AVX2 and RDSEED
Fix maintainer mode flags
Add AVX2 compiler flags for GCC and Clang. Tidy compiler option ordering.