Note platform-specific Foreign.C.Types in context
This should resolve #17335 (closed) by fixing the markup in the general note at the top of the Foreign.C.Types module. Haddock (usability trade-off), does not support multi-line emphasised text.
A note for each type mentions that it is platform-specific and links to the longer Platform Differences note at the top. Due to haddock markup limitations, the link text is just the module name, but I think it was possible to make it a reasonably natural part of the in-context note.