tag.hpp is invalid on C++17

[anntzer]

AFAICT

libasd/libasd/tag.hpp

Lines 17 to 23 in cceab73

	#if __cplusplus >= 201703L
	constexpr inline auto ch1 = channel<1>;
	constexpr inline auto ch2 = channel<2>;
	constexpr inline auto v0 = version<0>;
	constexpr inline auto v1 = version<1>;
	constexpr inline auto v2 = version<2>;
	#endif

is invalid; building with a C++17 compiler gives me

../../../libasd/tag.hpp:18:39: error: expected primary-expression before ‘;’ token
   18 | constexpr inline auto ch1 = channel<1>;
      |                                       ^
../../../libasd/tag.hpp:19:39: error: expected primary-expression before ‘;’ token
   19 | constexpr inline auto ch2 = channel<2>;
      |                                       ^
../../../libasd/tag.hpp:20:39: error: expected primary-expression before ‘;’ token
   20 | constexpr inline auto v0  = version<0>;
      |                                       ^
../../../libasd/tag.hpp:21:39: error: expected primary-expression before ‘;’ token
   21 | constexpr inline auto v1  = version<1>;
      |                                       ^
../../../libasd/tag.hpp:22:39: error: expected primary-expression before ‘;’ token
   22 | constexpr inline auto v2  = version<2>;
      |

[ToruNiina]

Fixed. thank you!