bin/rt should print password prompt to STDERR

[bartonski]

Ticket #34216: Feature request: bin/rt should print password prompt to STDERR

I've been using bin/rt in shell scripts, redirecting STDOUT to a file, or piping it to other processes. This will hang, waiting for a password prompt, if I haven't previously logged into rt.

Printing the password prompt to STDERR rather than STDOUT will send the password prompt to the screen, even if STDOUT is redirected, and also has the advantage of not polluting STDOUT with the password prompt.

This patch will cause the password prompt (as well as the 'Press CTRL-C if you do not want to continue' warning) to print to STDERR rather than STDOUT.