* Makefile (installed-stubs): New variable.
Set to $(inst_includedir)/gnu/stubs.h if $(biarch) is no,
or to $(inst_includedir)/gnu/stubs-$(biarch).h if otherwise.
[$(biarch) != no] (install-others-nosubdir): Add $(installed-stubs).
($(inst_includedir)/gnu/stubs.h): Use $(installed-stubs) for this
rule's target.
($(inst_includedir)/gnu/stubs.h): New target, install from ...
* include/stubs-biarch.h: New file.
* shlib-versions (i.86-.*-.*): Add WORDSIZE64 line mapping to x86_64.
* Makeconfig ($(common-objpfx)soversions.mk): Depend on Makeconfig.
Emit defn for variable `biarch'.
* include/stub-tag.h: Update comment.
