Patch to fix pxssh login to certain systems

Systems whose prompt ends with a $ or # without a following space will have nothing to read when synch_original_prompt tries to execute a read_nonblocking (to clear the buffer). Thus, the read times out. The attached patch adds a sendline() before the attempted read, to ensure that the buffer has something in it.

This fix is important because the default prompt on Ubuntu 8.04 server edition does not have a space after the $/#. This causes pxssh to fail on login.

An alternative solution would be to tell read_nonblocking to look for empty buffers instead of timing out, but in this case it is difficult to distinguish between a read that is taking a long time and one where there is no data to send.

The attached patch also checks for EOF on login in case the connection was abruptly closed.