Document limitation of our alignas() fallback.
Document limitation of our alignas() fallback.

We may define alignas(N) as __attribute__((aligned(N))) if C11's _Alignas
primitive is not available.  This older GCC feature only accepts a number
for N, not a type name.  Add some notes to m4/zw_alignment.m4 and the
generated config.h about this.

besser82/libxcrypt,besser82/libxcrypt,besser82/libxcrypt,besser82/libxcrypt