libstdc++: Replace uses of _GLIBCXX_USE_INT128 in testsuite

libstdc++: Replace uses of _GLIBCXX_USE_INT128 in testsuite

Since r12-435 the _GLIBCXX_USE_INT128 macro is never defined, so all
uses of it in the testsuite are wrong. The tests should be checking
__SIZEOF_INT128__ instead.

Also add some tests for an INT_3 type, which were missing.

libstdc++-v3/ChangeLog:

	* testsuite/18_support/numeric_limits/40856.cc: Replace use of
	_GLIBCXX_USE_INT128.
	* testsuite/18_support/numeric_limits/dr559.cc: Likewise.
	* testsuite/18_support/numeric_limits/lowest.cc: Likewise.
	* testsuite/18_support/numeric_limits/max_digits10.cc: Likewise.
	* testsuite/20_util/is_floating_point/value.cc: Likewise.
	* testsuite/20_util/is_integral/value.cc: Likewise.
	* testsuite/20_util/is_signed/value.cc: Likewise.
	* testsuite/20_util/is_unsigned/value.cc: Likewise.
	* testsuite/20_util/make_signed/requirements/typedefs-1.cc:
	Likewise.
	* testsuite/20_util/make_signed/requirements/typedefs-2.cc:
	Likewise.
	* testsuite/20_util/make_unsigned/requirements/typedefs-1.cc:
	Likewise.
	* testsuite/20_util/make_unsigned/requirements/typedefs-2.cc:
	Likewise.
	* testsuite/20_util/type_identity/requirements/typedefs.cc:
	Likewise.
	* testsuite/26_numerics/bit/bit.count/countl_one.cc: Likewise.
	* testsuite/26_numerics/bit/bit.count/countl_zero.cc: Likewise.
	* testsuite/26_numerics/bit/bit.count/countr_one.cc: Likewise.
	* testsuite/26_numerics/bit/bit.count/countr_zero.cc: Likewise.
	* testsuite/26_numerics/bit/bit.count/popcount.cc: Likewise.
	* testsuite/26_numerics/bit/bit.pow.two/bit_ceil.cc: Likewise.
	* testsuite/26_numerics/bit/bit.pow.two/bit_floor.cc: Likewise.
	* testsuite/26_numerics/bit/bit.pow.two/bit_width.cc: Likewise.
	* testsuite/26_numerics/bit/bit.pow.two/has_single_bit.cc:
	Likewise.
	* testsuite/26_numerics/bit/bit.rotate/rotl.cc: Likewise.

libstdc++-v3/ChangeLog:

	* testsuite/26_numerics/bit/bit.rotate/rotr.cc:
	* testsuite/util/testsuite_common_types.h: