  \/ F O - F O R G E T \/

Forgets a preceding DELETE command.

Parameters: none

 Providing no commands that amend or insert lines have been given, the last
DELETE command given is forgotten (i.e. undone). A message is output giving the
line # of the first line reinstated and the # of lines reinstated. If there are
no lines to reinstate (e.g. because of a MODIFY since the last DELETE) then a
message is output.
 It is designed to be used as follows: immediately after a DELETE, do a VIEW to
ensure that the correct lines have been deleted. If the wrong lines have been
deleted, do a FORGET.

File position
 The file is left at the 1st line reinstated
