Build build breakage in WinCNG backend caused when adding libssh2_userauth_publickey_frommemory.

The new feature isn't implemented for the WinCNG backend currently, but the WinCNG backend didn't contain any implementation of the required backend functions - even ones that returns an error.  That caused link errors.

This change fixes the problem by providing an implementation of the backend functions that returns an error.
1 file changed