Run the `Utilities/Scripts/clang-format.bash` script to update
all our C++ code to a new style defined by `.clang-format`.
Use `clang-format` version 3.8.
* If you reached this commit for a line in `git blame`, re-run the blame
operation starting at the parent of this commit to see older history
for the content.
* See the parent commit for instructions to rebase a change across this
style transition commit.
Exclude Ninja and Xcode from the CMP0021 test
They do not behave the same as the makefile generator with
relative paths.
Don't overwrite the header file for in-source builds.
Kitware Robot
Stephen Kelly