Preventing preemption of 'protected' symbols in GNU ld 2.26

[Cary Coutant]

> It would help me immensely on the GCC side if things if you and Alan could
> easily summarize correct behavior and the impact if we were to just revert
> HJ's change.  A testcase would be amazingly helpful too.

It looks like it's not just the one change. There's this patch:

   https://gcc.gnu.org/ml/gcc-patches/2015-07/msg01871.html

which took the idea that protected can still be pre-empted by a COPY
relocation and extended it to three more targets that use COPY
relocations.

I wonder how many other patches have been based on the same misunderstanding?

-cary