Fixed build when ENABLE_CLI_REMOTETCPFWD is the only allowed TCP forw…

which broken handling EAGAIN/EINTR

rather than SSH_OPEN_UNKNOWN_CHANNEL_TYPE

from Andrzej Szombierski

Print a message from configure if getpass() or crypt() were missing

if the system doesn't support getpass, we still default on the options
that require it which causes a build failure.  instead, only default
enable these when getpass is available.