Missing newtypes for socklen_t and nfds_t in System.Posix.Types
Motivation
The POSIX-specified types nfds_t and socklen_t are missing from System.Posix.Types. I've written bindings where I needed socklen_t before, but I was able to work around it since socklen_t is just a C int on every platform. However, this is not true for nfds_t. This type would be helpful for writing cross-platform bindings correctly.
Proposal
Add newtype CSocklen and newtype CNfds to System.Posix.Types in base. I'm happy to do this if others agree with the suggestion.