P0556R3 Integral power-of-2 operations, P0553R2 Bit operations

P0556R3 Integral power-of-2 operations, P0553R2 Bit operations

P0553R2 is not in the C++2a working draft yet, but is likely to be
approved soon. Neither proposal supports std::byte but this adds
overloads of each function for std::byte, assuming that will also get
added.

	* include/Makefile.am: Add new header.
	* include/Makefile.in: Regenerate.
	* include/precompiled/stdc++.h: Include new header.
	* include/std/bit: New header.
	(__rotl, __rotr, __countl_zero, __countl_one, __countr_zero)
	(__countr_one, __popcount, __ispow2, __ceil2, __floor2, __log2p1):
	Define for C++14.
	[!__STRICT_ANSI__] (rotl, rotr, countl_zero, countl_one, countr_zero)
	(countr_one, popcount): Define for C++2a. Also overload for std::byte.
	(ispow2, ceil2, floor2, log2p1): Define for C++2a.
	[!__STRICT_ANSI__] (ispow2, ceil2, floor2, log2p1): Overload for
	std::byte.
	* testsuite/26_numerics/bit/bit.pow.two/ceil2.cc: New.
	* testsuite/26_numerics/bit/bit.pow.two/floor2.cc: New.
	* testsuite/26_numerics/bit/bit.pow.two/ispow2.cc: New.
	* testsuite/26_numerics/bit/bit.pow.two/log2p1.cc: New.
	* testsuite/26_numerics/bit/bitops.rot/rotl.cc: New.
	* testsuite/26_numerics/bit/bitops.rot/rotr.cc: New.
	* testsuite/26_numerics/bit/bitops.count/countl_one.cc: New.
	* testsuite/26_numerics/bit/bitops.count/countl_zero.cc: New.
	* testsuite/26_numerics/bit/bitops.count/countr_one.cc: New.
	* testsuite/26_numerics/bit/bitops.count/countr_zero.cc: New.

From-SVN: r262360