RFC: Fix ia64 visibility

[Jim Wilson]

H. J. Lu wrote:
> On ia64, when we hide a symbol, we clear the want_plt2 field, but not
> want_plt. I don't see a reason not to. Also, if we don't need dynamic
> symbol lookup, which is true for symbols with non-default visibility,
> we should avoid it. Is this patch OK?

bfd is mostly a black box to me, but this stuff seems reasonable to me 
with your explanation.

want_plt2 is for dynamic symbols which are functions which need a full 
plt.  want_plt is for dynamic symbols which are not functions which need 
a minimal plt.  want_pltoff is for symbols, dynamic or not, which have 
pltoff relocations.  If a symbol is hidden, then we no longer need 
dynamic relocs, and hence want_plt should be cleared along with want_plt2.

The other bit is code that is simplying relocs if we don't need dynamic 
symbol lookup, which is the case for protected symbols, so that makes 
sense too.

Jim