The Xcode 'new build system' rejects empty signing identities unless
signing is explicitly marked as not allowed. Update test cases where we
turn off signing to explicitly disallow it too.
Also turn off signing in the XCTest test.
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.
