Squashed '3rd_party/libcxxrt/' content from commit b2396b5

git-subtree-dir: 3rd_party/libcxxrt
git-subtree-split: b2396b5945d7a2697c4762c3e52dc6f732b2eebd
Merge commit '3a0f1875fa1d8cd0569e36ba0bb13f3c4f4d01a8' as '3rd_party/libcxxrt'
Squashed '3rd_party/libcxx/' content from commit ddb4e4c

git-subtree-dir: 3rd_party/libcxx
git-subtree-split: ddb4e4cbb18d2006b356d37ca722249bbf9a8b86
Merge commit '30742bf3d7d5856f0ced811e43366effa8db53e7' as '3rd_party/libcxx'
initial import of the CMakeLists and example program