Posix.getFileStatus

[George Russell]

(1) I think Posix.getFileStatus should respond to a file which isn't there with something rather more helpful than
"system error".   For example, a "No such file or directory" message.

(2) The logical way of spotting whether a file is actually there is the
queryFile function, documented for example here:
    http://haskell.cs.yale.edu/ghc/docs/latest/html/hslibs/files-and-directories.html
But sadly the queryFile function does not appear to be in the Posix module!  At least not for
ghc5.04.2.

Good thing there's a Directory.doesFileExist function!  Of course that's not quite the same, since it
only checks if there is a normal file of that name (it returns False for a directory).