gold incremental file format on 64-bit

[Cary Coutant]

>> Is there anything else that's unaligned?
>
> Yes, some of the other sections can end up with an unaligned ending if
> there is an odd number of entries because the individual objects are a
> multiple of 4 bytes in size, but not a multiple of 8.

As far as I can tell, besides .gnu_incremental_inputs, the only other
section that has any address-sized items in it is
.gnu_incremental_relocs. That would probably be a bug in
Incremental_inputs::create_data_sections():

  this->relocs_section_ = new Output_data_space(4, "** incremental_relocs");

That "4" should be "size/8", where we'd determine "size" in the switch
statement above. That'll make sure the relocs section is properly
aligned.

-cary