IOCP.Winsock.Mswsock: define withPtrLen locally
IOCP.Winsock.Mswsock: define withPtrLen locally

I'm planning to split the network code out, so the network code can't depend on
windows-iocp internals.  This was the only point where the network modules
depended on an internal module of windows-iocp.

joeyadams/hs-windows-iocp