isPublicMember fails when member is an alias

[ReneZwanenburg]

The new isRWField doesn't work if the member string refers to an alias. For example:

struct S
{
  alias foo = float;
}

pragma(msg, isRWField!(S, "foo"));

source\vibe\internal\meta\traits.d(238): Error: argument float has no protection

It's the __traits(getProtection, MEM) in isPublicMember that blows up. I'm looking for a fix.

[ReneZwanenburg]

Done. I'll create a PR soon.