[PATCH v6] String: Add support for __memcmpeq() ABI on all targets

[Florian Weimer]

* Andreas Schwab:

> How about calling the function __memequal?

Programmers tend to use memequal for functions which return 0 for
different inputs:

| The consttime_memequal() function compares len bytes of memory at b1
| and b2 for equality, returning 0 if they are distinct and 1 if they
| are identical.

<https://man.netbsd.org/consttime_memequal.3>

Thanks,
Florian