Fix yaws_vdir.erl include directive

Recent versions of rebar were correctly unhappy with a malformed
include_lib in yaws_vdir.erl. Looks like this file was missed in a
previous edit to fix this problem. Changed to a regular include
instead, matching other source files.

src/yaws_vdir.erl

@@ -2,7 +2,7 @@
 
 -export([arg_rewrite/1]).
 
--include_lib("../include/yaws_api.hrl").
+-include("../include/yaws_api.hrl").
 
 -export([join/2]).