Fix include statement of in6addr.h

Only include it when CMake can find it. This works with MinGW and WinCE.
Fix compilation on Windows CE after cleanup
Declare the lws_ssl_capable_*_no_ssl function outside the SSL #ifdef

This avoids a compiler warning about a not declared function.
Windows: Fix the passed parameter to the setsockopt function

This avoids compiler warnings about missmatched parameter types.
Windows: Use gai_strerrorW() instead of gai_strerror()

This allows compilation on Windows CE too.
Windows: Fix implementation of lws_plat_inet_ntop()

We need to pass a sockaddr_in6 struct to WSAAddressToString() to have a
working implementation for IPV6. Also use the WideChar version to allow
compilation on Windows CE too.