Introduce prototype-style function definition for wcscpy on 32-bit

POWER.  The old-style function definition was removed upstream in:

commit 93be09e7259caf227dd586404f3c74b61c830cb4

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

Date:   Mon Oct 14 09:43:31 2013 -0500

    PowerPC: multiarch wcscpy for PowerPC32

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

index 9bd907788e6f2337..0af09793f7ce43e0 100644

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

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

@@ -22,9 +22,7 @@

 /* Copy SRC to DEST.  */

 wchar_t *

-wcscpy (dest, src)

-     wchar_t *dest;

-     const wchar_t *src;

+wcscpy (wchar_t *dest, const wchar_t *src)

 {

   wint_t c,d;

   wchar_t *wcp, *wcp2;