[Issue 19412] std.algorithm.cmp with default ordering can use memcmp for all big-endian or size 1 unsigned types (instead of just char)

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19412

--- Comment #3 from Nathan S. <n8sh.secondary at hotmail.com> ---
Benchmarking shows that whether memcmp is an improvement or not for
wider-than-byte types depends on input length, so this is conservatively being
changed to just unsigned byte-width types.

--