Flush Duplicate Lines

["Frank J. Wancho" <WANCHO@SIMTEL20.ARPA>]

Every so often I've wished for a Flush Duplicate Lines function, and
was surprised to find that none existed as such.  I needed one last
night and found the following in LONG-FILENAMES.EMACS, which I
manually entered in a minibuffer, and it worked just fine!

Would some EMACS maintainer please consider fixing up this function
and entering it into the basic set?

(Note that this function depends on the lines being sorted and does
the sort, and that the following is the graphic, not actual code)

bj
^P$l$$ bj
< .-z; x1
 <
   :s
^]^S1$;-k 0:l>
 l>

Primitive, but functional.

--Frank