[libstdc++ patch] Fix to std::equal and bug c++/2406

[Gabriel Dos Reis]

Joe Buck <jbuck@racerx.synopsys.com> writes:

| See discussion on libstdc++ list.  This is to fix c++/2406.
| Papers not on file, but according to RMS this doesn't matter for a one liner.
| 
| 2001-04-03  Joe Buck  <jbuck@welsh-buck.org>
| 
| 	* stl_algobase.h (std::equal): avoid use of possibly-undefined
| 	operator != (one line patch).

This was pre-approved. 

-- Gaby