Refactor low level I/O traffic accounting

[yadij]

Perform the FD read/write byte counting in the class fde read/write methods instead of having the callers perform manual accounting with fd_bytes().

This fixes traffic double-counting in FTP and under-counting of UDP protocols, Disker I/O, possibly TLS tunnels as well.

Also, resolves MinGW-w64 symbol collisions between winnt.h definitions and FD_READ/RD_WRITE enums.