Fix build warnings on Windows.
Fix build warnings on Windows.

rofl0r/libssh,mwgoldsmith/ssh,nviennot/libssh,wangshawn/libssh,miloj/libssh-v0.5,bigcat26/libssh-mod,taikoo/libssh,mwgoldsmith/libssh,jt1/honeypot-libssh,jt1/honeypot-libssh,nviennot/libssh,robxu9/libssh,elastichosts/libssh,wangshawn/libssh,miloj/libssh-v0.5,taikoo/libssh,Distrotech/libssh,jahrome/libssh,mwgoldsmith/libssh,jt1/honeypot-libssh,rofl0r/libssh,pouete/libssh,pouete/libssh,wangshawn/libssh,DouglasHeriot/libssh,elastichosts/libssh,robxu9/libssh,miloj/libssh-v0.5,substack/libssh,substack/libssh,mwgoldsmith/ssh,sebadoom/libssh,mwgoldsmith/libssh,nviennot/libssh,kedazo/libssh,DouglasHeriot/libssh,sebadoom/libssh,miloj/libssh-v0.5,DouglasHeriot/libssh,Distrotech/libssh,rofl0r/libssh,nviennot/libssh,substack/libssh,jahrome/libssh,jahrome/libssh,taikoo/libssh,mwgoldsmith/ssh,kedazo/libssh,rofl0r/libssh,sebadoom/libssh,sebadoom/libssh,DouglasHeriot/libssh,kedazo/libssh,kedazo/libssh,pouete/libssh,elastichosts/libssh,Distrotech/libssh,bigcat26/libssh-mod,mwgoldsmith/ssh,jt1/honeypot-libssh,robxu9/libssh,pouete/libssh,bigcat26/libssh-mod,robxu9/libssh,jahrome/libssh,Distrotech/libssh,bigcat26/libssh-mod,mwgoldsmith/libssh,substack/libssh,wangshawn/libssh,taikoo/libssh