Run clang-tidy on all source files under `clang-tools-extra/clang-tidy`
with `-header-filter=clang-tidy.*` and make suggested corrections.
Differential Revision: https://reviews.llvm.org/D112864
This patch adds bugprone-reserved-identifier, which flags uses of __names _Like
::_this, which are reserved for the implementation. The check can optionally be
inverted, i.e. configured to flag any names that are _not_ reserved, which may
be useful for e.g. standard library implementors.