Fix powerpc64le problem from last ldbl-opt patch [committed]

[Gabriel F. T. Gomes]

On 18 Sep 2017, Joseph Myers wrote:

>This patch fixes a problem on powerpc64le that I missed in initial
>testing of my last patch to ldbl-opt.  In the specific case of
>powerpc64le, the weak aliases for exp10l and remainderl do not get
>defined in the generic wrappers because of how those wrappers
>undefine and redefine weak_alias.  This patch restores those aliases
>in the ldbl-opt code.
>
>Tested (compilation only) for powerpc64le with build-many-glibcs.py.  
>Committed.

Thanks for doing this.
I tested (make check) for powerpc64le and it indeed fixes the problem with
exp10l and remainderl.