PR tree-optimization/21088
	* fold-const.c (fold_unary, fold_binary, fold_ternary):
	Export.
	* tree-vrp.c (compare_values): Use fold_binary to compare
	pointers.  Use boolean_type_node as the type of a comparison
	expression being folded.
	* tree.h: Add prototypes for fold_unary, fold_binary,
	fold_ternary.

From-SVN: r98600