Add a getopt flag that consumes all remaining arguments

On Unix, some programs run other programs. It is standard convention to pass along the tail of the command line unprocessed.

Examples:

bash -c command [args]
time command [args]
schedtool -e command [args]
chroot /newroot command [args]

[alexcrichton]

cc @nick29581, could this be migrated to https://github.com/rust-lang/getopts?

[rust-highfive]

This issue has been moved to the RFCs repo: rust-lang/getopts#6