cleanup wcstombs

remove redundant headers and comments; this file is completely trivial
now. also, avoid temp var.

src/multibyte/wcstombs.c

@@ -1,18 +1,7 @@
-/* 
- * This code was written by Rich Felker in 2010; no copyright is claimed.
- * This code is in the public domain. Attribution is appreciated but
- * unnecessary.
- */
-
 #include <stdlib.h>
-#include <inttypes.h>
 #include <wchar.h>
-#include <errno.h>
-
-#include "internal.h"
 
 size_t wcstombs(char *restrict s, const wchar_t *restrict ws, size_t n)
 {
-	const wchar_t * x = ws;
-	return wcsrtombs(s, &x, n, 0);
+	return wcsrtombs(s, &(const wchar_t *){ws}, n, 0);
 }