Enable 0x10 alignment for aarch64 symbols as is done for x86_64

[Cary Coutant]

> and if I have set has_code_fill in aarch64.cc to true already and am
> getting the same result?

I assume you've also implemented Target_aarch64::do_code_fill()?

There could be several reasons. Maybe there isn't any padding in your
.text section (because there are no input sections with an alignment
that would require padding). Maybe the input sections aren't being
stored individually (because, e.g., they don't need sorting), in which
case, any fills are handled by the separate list of fills.

-cary