install the shared libgcc

[Brian R. Gaeke]

And then spake Richard Henderson, as follows:
>         * Makefile.in (slibdir): New variable.
>         (libgcc.mk): Pass SHLIB_INSTALL to mklibgcc.
>         (installdirs): Create slibdir.
>         (install-libgcc, install-multilib): Defer to libgcc.mk.
>         * configure.in (slibdir): Substitute.
>         * mklibgcc.in (install): New target.

I had to apply the attached patch and re-run autoconf to get configure
to work (otherwise it loops forever running "yes = yes", because M4 eats
the [ and ] in configure.in before they get to configure.)

Hope this helps.

-Brian