Use pre-increment operators for better performance

Though any decent compiler would optimise away the difference anyway.
Correct lock_guard post-increment signatures (#1)

Thanks clang for pointing this one out :)
Fix another clang-specific build issue (#1)

It's less clear whether or not this one was a real issue or just clang
being pedantic. But either way, the solution is a small improvement.
Merge branch 'master' of github.com:pcolby/dye