Handle typedef of opaque structs

[biozic]

When an opaque struct is defined in a C header like that:

    typedef struct foo foo;

no symbols are generated in the .d file. It only works if the name of the struct is not the same as the typedef. The output should be:

   struct foo;

[ciechowoj]

Yeah, that's embarrassing.

[ciechowoj]

I should fix it in a moment.