how to resolve Windows pathnames into cygwin ones

[mgierdal at gmail.com]

I am looking for a function to resolve 'F:/foo/bar' into '/cygdrive/f/
foo/bar'. I get the original dirpath from tkFileDialog.askdirectory in
a Windows form and none of os.path.* functions seem to resolve it to a
cygwin form. Rather they _append_ it to the current directory,
resulting at best in a monster '/cygdrive/c/whatever/f/foo/bar'.
It's all being developed under cygwin currently (so it is a kind of
mixed environment), but I would like the fix to work correctly in any
environment.

Thanks,
Marcin