Port the http interface to the Lua Interface Module framework.

 * share/luaintf/http.lua: Equivalent of the legacy modules/control/http/
   module. (The new module takes 272 lines of Lua, instead of 5475 lines for
   the old one.) Functionality is basically the same except for CGI support
   which is missing.
 * share/http-lua/: The HTML files using the new <?vlc [lua code] ?> syntax.
 * modules/misc/lua/: Add Lua bindings for a few VLC function, the most
   important being the HTTPd high level functions, ACLs, stat and opendir.

The Lua code still needs to be cleaned up a bit.