[PATCH] Introduce new gold plugin option "relocation-pic"

[Rafael Espíndola]

> I don't understand how it could be fixed.
> When compiler generates object it has no information regarding further usage
> of object: executable or library.
> Function isPIEDefault turns on PIE for every object for specific target.
> So it seems to be useful only for targets with no shared libraries.

I think isPIEDefault and isPICDefault should interact in the same way
as -fPIC and -fPIE: PIC wins since it is the most restrictive and we
can just just define both.

But that can really be another patch. For now just have a comment
saying why you can't use isPIEDefault.

Cheers,
Rafael