(va_arg, mips3 case): Use __PTRDIFF_TYPE__ not int in casts.

From-SVN: r8716

gcc/ginclude/va-mips.h

@@ -66,11 +66,11 @@ void va_end (__gnuc_va_list);		/* Defined in libgcc.a */
 #if __mips==3
 #ifdef __MIPSEB__
 #define va_arg(__AP, __type)                                    \
-  ((__type *) (void *) (__AP = (char *) ((((int)__AP + 8 - 1) & -8) \
+  ((__type *) (void *) (__AP = (char *) ((((__PTRDIFF_TYPE__)__AP + 8 - 1) & -8) \
 					 + __va_rounded_size (__type))))[-1]
 #else
 #define va_arg(__AP, __type)                                    \
-  ((__AP = (char *) ((((int)__AP + 8 - 1) & -8)			\
+  ((__AP = (char *) ((((__PTRDIFF_TYPE__)__AP + 8 - 1) & -8)	\
 		     + __va_rounded_size (__type))),		\
    *(__type *) (void *) (__AP - __va_rounded_size (__type)))
 #endif