Introduce prototype-style function definition for 32-bit POWER wcsrchr.

Upstream removed the old-style function definition in:

commit bb04e529f60df7138a4fe5f1ed016dd87ade59a3

Author: Adhemerval Zanella <azanella@linux.vnet.ibm.com>

Date:   Mon Oct 14 09:26:07 2013 -0500

    PowerPC: multiarch wcsrchr for PowerPC32

diff --git a/sysdeps/powerpc/powerpc32/power6/wcsrchr.c b/sysdeps/powerpc/powerpc32/power6/wcsrchr.c

index 333650190afff171..4deb44966915679f 100644

--- a/sysdeps/powerpc/powerpc32/power6/wcsrchr.c

+++ b/sysdeps/powerpc/powerpc32/power6/wcsrchr.c

@@ -21,9 +21,7 @@

 /* Find the last occurrence of WC in WCS.  */

 wchar_t *

-wcsrchr (wcs, wc)

-     const wchar_t *wcs;

-     const wchar_t wc;

+wcsrchr (const wchar_t *wcs, const wchar_t wc)

 {

   const wchar_t *wcs2 = wcs + 1;

   const wchar_t *retval = NULL;