libiberty: dupargv: rewrite to use xstrdup

This func is basically open coding the xstrdup function, so gut it
and use that directly.

From-SVN: r232086

libiberty/ChangeLog

+2016-01-05  Mike Frysinger  <vapier@gentoo.org>
+
+	* argv.c (dupargv): Replace strlen/xmalloc/strcpy with xstrdup.
+
 2015-12-28  Patrick Palka  <ppalka@gcc.gnu.org>
 
 	* crc32.c: In the documentation, don't refer to GDB's

libiberty/argv.c

@@ -76,11 +76,7 @@ dupargv (char **argv)
 
   /* the strings */
   for (argc = 0; argv[argc] != NULL; argc++)
-    {
-      int len = strlen (argv[argc]);
-      copy[argc] = (char *) xmalloc (len + 1);
-      strcpy (copy[argc], argv[argc]);
-    }
+    copy[argc] = xstrdup (argv[argc]);
   copy[argc] = NULL;
   return copy;
 }