[PATCH] Enable building glibc with gold.

[Roland McGrath]

I did most of the work for this a long time ago.  See the
roland/gold-vs-libc branch for the version-number checking piece that was
the only remaining thing.  Last time I tried that there were some problems
with some of the DSOs produced and I didn't look into it further, e.g. to
determine if a newer gold than the one I used then worked better, or what
the differences between the BFD-produced objects and the Gold-produced ones
were.

I'd certainly prefer that we not have configure deciding whether it thinks
the linker is Gold or not.

--with-default-link when the automatic configure test fails still produces
working binaries, just with perhaps suboptimal layout.  So I don't think
there is really any need for extra checks about that.