sh: Add a prototype for the gcc __set_fpscr internal function

The sh port uses the gcc __set_fpscr internal function, but neither gcc
nor glibc creates a prototype for it.  This leads to a bunch of random
warnings about implicit decls during the build.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>

libc/sysdeps/linux/sh/fpu_control.h

@@ -1,5 +1,5 @@
 /* FPU control word definitions.  SH version.
-   Copyright (C) 1999, 2000 Free Software Foundation, Inc.
+   Copyright (C) 1999, 2000, 2009 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -47,6 +47,8 @@ typedef unsigned int fpu_control_t;
 #define _FPU_GETCW(cw) __asm__ ("sts fpscr,%0" : "=r" (cw))
 
 #if defined __GNUC__
+/* GCC provides this function */
+extern void __set_fpscr (unsigned long);
 #define _FPU_SETCW(cw) __set_fpscr ((cw))
 #else
 #define _FPU_SETCW(cw) __asm__ ("lds %0,fpscr" : : "r" (cw))