Adds enhanced autotools build system used by openthread and openweave projects:

* Package management: 'make dist' and 'make distcheck'
* Cross-platform handling: (Linux, Darwin, iOS, Android, embedded arm, etc.)
* Multiple compiler support: clang, GCC
* Integrates automated testing framework: 'make check'
* Code style enforcement: 'make pretty' and 'make pretty-check' integration with clang-format