[patch] Don't compute a "patched" storage class

[Rafael Espíndola]

>> The linkage spec decl (only the variant without braces) seems to propagate its "extern" keyword down to the inner decl as a *written* storage class. I guess this is not really meant.
>
>
> No, this is an anachronism from the days prior to linkage computation. I think it can be zapped.

To be clear, getStorageClass should return SC_None for

extern "C" void foo();

and we should have a separate bit for isSingleLineExternC (to
implement [dcl.link] p7). Correct?

>         - Doug

Cheers,
Rafael