r218141 - In the Itanium ABI, move stuff to the comdat of variables with static init.

[Rafael Espíndola]

> ... and we may want an external_odr for external definitions in comdats.
> Yuck.

Yuck indeed.

We are probably better off keeping the number of linkages down for
now. At some point it might be a good idea to revisit the design and
maybe split it in some orthogonal dimensions (odr, can_be_dropped,
weak/strong, etc), but it would be nice to let the dust of the comdat
support settle first.

Cheers,
Rafael