[Bug libstdc++/49559] stable_sort calls self-move-assignment operator

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49559

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-06-28 
08:56:39 UTC ---
bah, that's testing the wrong thing
the test should be:
      if (__result == __last)
        return __first;