to use connection_send directly.

Rev: src/channel.c:1.122
Rev: src/channel_commands.c:1.30
Rev: src/client.c:1.155
Rev: src/client_pty.c:1.27
Rev: src/client_userauth.c:1.56
Rev: src/connection.c:1.76
Rev: src/connection.h:1.69
Rev: src/gateway_channel.c:1.18
Rev: src/proxy.c:1.18
Rev: src/proxy_userauth.c:1.15
Rev: src/server.c:1.75
Rev: src/server_session.c:1.101
Rev: src/server_userauth.c:1.42