Deletes the file specified by filespec.
If the filespec designator is an open stream,
then filespec and the file associated with it are affected
(if the file system permits),
in which case filespec might be closed immediately,
and the deletion might be immediate or delayed until filespec is explicitly closed,
depending on the requirements of the file system.
It is implementation-dependent whether an attempt
to delete a nonexistent file is considered to be successful.
delete-file returns true if it succeeds,
or signals an error of type file-error if it does not.
The consequences are undefined
if filespec has a wild component,
or if filespec has a nil component
and the file system does not permit a nil component.