(lsftp_rl_completion): Use const argument.
(lsftp_rl_command_generator): Likewise.
(lsftp_rl_remotefile_generator): Likewise.
(lsftp_rl_no_generator): Likewise.
(lsftp_rl_history_fname): Deleted unused local variable username.

* rl.h: Use libreadline typedefs when declaring callback
functions.

Rev: sftp/ChangeLog:1.7
Rev: sftp/rl.c:1.2
Rev: sftp/rl.h:1.2