Changed getmntent behavior

[Christopher Faylor]

I reinstated some old behavior of the getmntent() function (for those
who played with snapshots in 1999).

getmnent now returns all of the drives in your system in /cygdrive/n
format.

This means that mount and df will report all of your available drives.

I'd like comments on this.  Does it make mount too wordy?  Personally
I think it is pretty useful but I guess I need feedback.

cgf