windows: Also delete old .pdb files before compiling
windows: Implement putenv for WDK builds

Also make MinGW's putenv behave as its Linux counterpart.
windows: Update libusb fork to 1.0.18

This includes two fixes for Intel and AMD USB 3.0 hubs.
Extend client info logging to include socket type and authentication state
Restructure socket accept handling

Replace the accept_epilog function by an allocate function. This allows
the socket_accept function to allocate a new client socket on its own
without the need to have an correctly allocated socket passed to it.

Also remove the unused websocket_create function.