Merge topic 'clang-format-source'

d9fd2f54 Revise C++ coding style using clang-format
82df6dea Empty commit at end of history preceding clang-format style transition
6a13f43f CONTRIBUTING: Add a section on coding style
bf451d9f Add a script to run clang-format on the entire source tree
1e90d78f Configure clang-format for CMake source tree
da60adc3 Tell Git to use a distinct conflict marker size in `.rst` files