PR middle-end/23673
	* fold-const.c (fold_binary) <EQ_EXPR>:  Fold (X^Y) == 0 as X == Y
	and (X^Y) != 0 as X != Y.  Fold (X^Y) == Y as X == 0, and some
	symmetry related transformations.  Fold (X^C1) == C2 as
	X == (C1^C2).

	* gcc.dg/fold-eqxor-1.c: New test case.
	* gcc.dg/fold-eqxor-2.c: Likewise.
	* gcc.dg/fold-eqxor-3.c: Likewise.

From-SVN: r111442