stdio: Make sure __VALIST is defined in stdio.h

This is needed for the newlib stdio API.

Signed-off-by: Keith Packard <keithp@keithp.com>

Author: keith-packard

newlib/libc/stdio/stdio.h

@@ -155,6 +155,14 @@ typedef _fpos64_t fpos64_t;
  * Functions defined in ANSI C standard.
  */
 
+#ifndef __VALIST
+#ifdef __GNUC__
+#define __VALIST __gnuc_va_list
+#else
+#define __VALIST char*
+#endif
+#endif
+
 #if __POSIX_VISIBLE
 char *	ctermid (char *);
 #endif
@@ -629,7 +637,7 @@ FILE *_fopencookie_r (struct _reent *, void *__cookie,
 
 #ifndef __CUSTOM_FILE_IO__
 /*
- * The __sfoo macros are here so that we can 
+ * The __sfoo macros are here so that we can
  * define function versions in the C library.
  */
 #define       __sgetc_raw_r(__ptr, __f) (--(__f)->_r < 0 ? __srget_r(__ptr, __f) : (int)(*(__f)->_p++))
@@ -638,7 +646,7 @@ FILE *_fopencookie_r (struct _reent *, void *__cookie,
 /*  For a platform with CR/LF, additional logic is required by
   __sgetc_r which would otherwise simply be a macro; therefore we
   use an inlined function.  The function is only meant to be inlined
-  in place as used and the function body should never be emitted.  
+  in place as used and the function body should never be emitted.
 
   There are two possible means to this end when compiling with GCC,
   one when compiling with a standard C99 compiler, and for other