type_traits (result_of): Provide "SFINAE-friendly" (see N3436) implementation.

type_traits (result_of): Provide "SFINAE-friendly" (see N3436) implementation.

2012-10-01  Daniel Krugler  <daniel.kruegler@googlemail.com>

	* include/std/type_traits (result_of): Provide "SFINAE-friendly"
	(see N3436) implementation.
	* testsuite/20_util/result_of/sfinae_friendly_1.cc: New.
	* testsuite/20_util/result_of/sfinae_friendly_2.cc: Likewise.
	* testsuite/20_util/make_signed/requirements/typedefs_neg.cc: Tweak
	dg-error line numbers.
	* testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc:
	Likewise.
	* testsuite/20_util/declval/requirements/1_neg.cc: Likewise.

From-SVN: r191930