Squashed 'src/floobits/common/' changes from 3d6baef..3237d36

3237d36 remove imports from outside common
26ee106 fold threadsafety into context

git-subtree-dir: src/floobits/common
git-subtree-split: 3237d36fc758eb30fb3425c6d720ae52d60dcfc6
Merge commit '15fdca0fea69c763f2a80f858f6df0ed51303a96'