Run clang-format
Merge clang-format from core
Run clang-format
Rename regex.h and regex.cpp to regex_yaml, so they don't interfere with the posix variant
Add gtest, as separate set of tests (that just follow the ad-hoc tests that already exist)
Merge gtest from core
Fix SEGV in ostream_wrapper
Add more ostream_wrapper tests
Merge ostream_wrapper fix from core
Add missing includes to node_data.h
Run IWYU
Merge IWYU from core
Run IWYU
Add missing include to read.cpp
Merge read fix from core
Add missing include to otream_wrapper
Merge ostream_wrapper fix from core
Add test for cloning a null node
Move EmitterTests to gtest
Merge from core