* fold-const.c (omit_two_operands): New function.
	* tree.h (omit_two_operands): Prototype here.
	* builtins.c (fold_builtin_unordered_cmp): New function to lower
	C99 unordered comparison builtins to the appropriate tree nodes.
	(fold_builtin_1): Use fold_builtin_unordered_cmp to lower
	BUILT_IN_ISGREATER, BUILT_IN_ISGREATEREQUAL, BUILT_IN_ISLESS,
	BUILT_IN_ISLESSEQUAL and BUILT_IN_ISLESSGREATER.  Manually lower
	BUILT_IN_ISUNORDERED comparisons to an UNORDERED_EXPR tree node.
	(simplify_builtin_memcmp, simplify_builtin_strncmp,
	simplify_builtin_strncat, simplify_builtin_strspn): Use the new
	omit_two_operands function to build the required COMPOUND_EXPRs.

From-SVN: r83040