[plt-scheme] MzScheme and read-line

Invoking (read-line) in DrScheme behaves as I would expect -- it
doesn't return until a newline is read.  However, invoking (read-line)
in MzScheme (on Win7) return "\r" immediately without waiting for any
input.  I've tried this before and after loading the GNU readline
support with no change in behavior.  I have verified that the current
port is a terminal port in the interactive session and I've tried
starting MzScheme with and without "-i".  Thanks.

-- Eric