[libcxx] [test] Fix the classic_table test on Windows

On Windows, constants like F::alpha and F::print are bitmasks
consisting of multiple bits (e.g. F::alpha consisting of both the
bits F::upper and F::lower). In such a case, we can't check that
all the bits from all the expected constants are set. Instead,
check that (p[i] & mask) != 0 returns the expected value.

Differential Revision: https://reviews.llvm.org/D120802