More setup changes

[Chris Faylor]

I have modified setup to always try to set the write bit on the files that
it extracts.  To do this, I had to monitor tar's output so I took the
opportunity to build a list of files on the fly rather than reading this
from a file.

I also start up cygpath in the background so that it can be used as a
"filename translation engine".  cygpath can now accept filenames on
its stdin, spitting out translated filenames to stdout.

The end result is that I think that setup is quite a bit faster now.
The creation of the uninstall bat file is fast enough that it doesn't
make sense to track its progress.

setup's log file is now serves no function other than to monitor the
files that have been extracted.  If there are error messages, I write
them to both the log file and to stderr.

Corinna, I would be interested in hearing if this version of setup
works better for you.

cgf