[libc] Add implementations of remquo[f|l] and remainder[f|l].

[sivachandra]

Summary

The implementation is not fully standards compliant in the sense that
errno is not set on error, and floating point exceptions are not raised.

Subnormal range and normal range are tested separately in the tests.

[lntue]

libc/utils/FPUtil/DivisionAndRemainderOperations.h

74

When the remainder is in the subnormal range, I think the final check below is correct, but with an implicit assumption that the rounding from NormalFloat<T> to T is truncation.
Can you add that to comments, in case we change the rounding NormalFloat<T> to T to the default round-to-nearest, tie-to-even? So that at least we will add more tests for subnormal range to make sure that it still works correctly, even when NormalFloat<T> rounding is updated.

[sivachandra]

Add comment as suggested.

[sivachandra]

Added comment as suggested.