doc: Document new meaning of SSH_BIND_OPTIONS_HOSTKEY
doc: Document new meaning of SSH_BIND_OPTIONS_HOSTKEY

Signed-off-by: Alan Dunn <90d3ad16cd4565f91305ac667132a38a0361079b@gmail.com>
Reviewed-by: Andreas Schneider <5be00ddc76278cf6077f5047ca3384a88460c671@cryptomilk.org>

robxu9/libssh,nviennot/libssh,taikoo/libssh,pouete/libssh,kedazo/libssh,kedazo/libssh,sebadoom/libssh,kedazo/libssh,elastichosts/libssh,elastichosts/libssh,Distrotech/libssh,mwgoldsmith/libssh,DouglasHeriot/libssh,pouete/libssh,robxu9/libssh,nviennot/libssh,robxu9/libssh,taikoo/libssh,wangshawn/libssh,robxu9/libssh,mwgoldsmith/libssh,DouglasHeriot/libssh,wangshawn/libssh,mwgoldsmith/ssh,sebadoom/libssh,sebadoom/libssh,Distrotech/libssh,wangshawn/libssh,mwgoldsmith/libssh,DouglasHeriot/libssh,kedazo/libssh,mwgoldsmith/libssh,taikoo/libssh,sebadoom/libssh,nviennot/libssh,DouglasHeriot/libssh,pouete/libssh,Distrotech/libssh,mwgoldsmith/ssh,elastichosts/libssh,mwgoldsmith/ssh,mwgoldsmith/ssh,wangshawn/libssh,taikoo/libssh,pouete/libssh,nviennot/libssh,Distrotech/libssh