_scanf.c: fix to signedness warnings

Signed-off-by: Peter S. Mazinger <ps.m@gmx.net>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

libc/stdio/_scanf.c

@@ -377,9 +377,9 @@ int vswscanf(const wchar_t * __restrict str, const wchar_t * __restrict format,
 	FILE f;
 
 	f.__bufstart =
-	f.__bufpos = (char *) str;
+	f.__bufpos = (unsigned char *) str;
 	f.__bufread =
-	f.__bufend = (char *)(str + wcslen(str));
+	f.__bufend = (unsigned char *)(str + wcslen(str));
 	__STDIO_STREAM_DISABLE_GETC(&f);
 	__STDIO_STREAM_DISABLE_PUTC(&f);