gold's target->make_symbol()

[David Miller <davem at davemloft dot net>]

Gold has a target hook that seems to exist to facilitate the things
that BFD elf backends use the BFD add symbol hook for.

I need to use this to add proper support for STT_REGISTER symbols on
sparc.

But it's missing arguments :-) For example a reference to the symbol
table entry isn't even provided.  I guess this was just never
finished.

There are two call sites for this target hook, one has a symtab
reference available, the second does not.  But in the second case I
don't think the hook is even needed as that function
Symbol_table::define_special_symbol() probably does run for cases the
target would care about.  Furthermore we would need to pass different
args as a elfcpp::Sym to parse isn't available in this case.