Fix some broken documentation comments
Fix some broken documentation comments

Summary: I temporarily enabled Clang's `-Wdocumentation` flag, which reports things like using an `param` for a parameter that doesn't exist. [Full explanation with examples here](https://clang.llvm.org/docs/DiagnosticsReference.html#wdocumentation).

Reviewed By: yfeldblum

Differential Revision: D21396362

fbshipit-source-id: d7b34bc14af7bb1b0901a8f195c02674eb587fbc

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly