Check error codes

[Dennis Payne <payned@rpi.edu>]

An interesting bug was sent to me by Andrei Malyshev.  Xwpe would
delete whatever directory it started in.  This is because on line 1168
in we_fl_unix.c the program attempts to change directory to the
wastebasket and then get it path.  However, the code doesn't check for
errors.  If the change directory fails which it did for Andrei, xwpe
will get back the starting directory as the path for the wastebasket.
On exit it then destroys all files in the wastebasket.

Always remember to check error codes.

Dennis Payne
payned@rpi.edu