The DeleteFile method deletes an existing file from the
remote server.
Note that you must have the appropriate permission to delete the
file, or an error will occur.
Note that this "remote file management" method of the File
Transfer control MAY be supported for some HTTP servers as well as
for FTP servers.
The Filename argument specifies the name of the file to
delete on the remote host.
A value of zero is returned if the operation was successful,
otherwise a non-zero error code is returned which indicates the
cause of the failure.