Cygwin: try_to_bin: don't check recycler filename all the time

Cygwin: try_to_bin: don't check recycler filename all the time

So far we check the recycler name all the time, and the last interation
also only managed to handle two ways to write the recycler.  However,
an adventurous user might change the case of the recycler arbitrarily.

Fix this problem by keeping track of the name in a somewhat relaxed
fashion.  Use camel back on drive C by default, all upper case elsewhere.
Only if the rename op fails do we fix the recycler name on the fly
when trying to create it, and it turns out it already existed.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>