Reenabled non-const reference checking in check_style.sh, fixed newly discovered problems.
Removed TODO about whitespace/forcolon.
Fixed the remaining non-const references.
Fixed some indentation problems.
Reenabled runtime/explicit style checks and fixed newly discovered problems.
Removed readability/braces disablement from check_style.sh.
Put in a bunch of comments marking the end of namespaces.
Removed build/include_what_you_use nolint declarations.
Removed a bunch of untagged NOLINT comments.