Prevent module import inside @implementation

[Ben Langmuir]

On Feb 3, 2014, at 5:17 PM, Richard Smith <richard at metafoo.co.uk> wrote:

> Moving parsing for annot_module_include from ParseTopLevelDecl to ParseExternalDeclaration does not seem right to me -- we only want to allow module imports at the top level. (This patch appears to allow them in namespaces and extern "C" contexts.)
> 

I guess I shouldn't have assume that the handling of @import was correct.  I will move parsing for both implicit and explicit imports to top level.  That may expose some more cases that need better diagnostics.

Thanks,

Ben