type_traits (common_time): Provide "SFINAE-friendly" implementation.

type_traits (common_time): Provide "SFINAE-friendly" implementation.

2012-10-09  Daniel Krugler  <daniel.kruegler@googlemail.com>

	* include/std/type_traits (common_time): Provide "SFINAE-friendly"
	implementation.
	(__success_type, __failure_type): Fix.
	* include/std/chrono (common_type): Likewise for the chrono::time_point
	specialization.
	* testsuite/20_util/common_type/requirements/sfinae_friendly_1.cc: New.
	* testsuite/20_util/common_type/requirements/sfinae_friendly_2.cc:
	Likewise.
	* testsuite/20_util/duration/requirements/sfinae_friendly_1.cc:
	Likewise.
	* testsuite/20_util/common_type/requirements/typedefs-1.cc: Adjust wrt
	LWG 2141.
	* testsuite/20_util/duration/requirements/typedefs_neg1.cc: Adjust
	dg-error line numbers.
	* testsuite/20_util/duration/requirements/typedefs_neg2.cc: Likewise.
	* testsuite/20_util/duration/requirements/typedefs_neg3.cc: Likewise.
	* testsuite/20_util/make_signed/requirements/typedefs_neg.cc: Likewise.
	* testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc:
	Likewise.
	* testsuite/20_util/declval/requirements/1_neg.cc: Likewise.

	* testsuite/20_util/result_of/sfinae_friendly_1.cc: Trivial stylistic
	tweaks.
	* testsuite/20_util/result_of/sfinae_friendly_2.cc: Likewise.

From-SVN: r192276