Give the "cannot pass object of non-POD type 'class C' through variadic...

Give the "cannot pass object of non-POD type 'class C' through variadic constructor; call will abort at runtime" warning a -W flag (non-pod-varargs) and default it being an error by default.  There is no good reason to allow users to get bitten by this sort of thing by default.

llvm-svn: 91094