add 2.4 support

commit e246940c2e74a897fca1f9ca04855645aaef0dd3
Author: Stan Hutcheon <stanhutcheon@bigfork.co.uk>
Date:   Thu Oct 30 11:28:48 2014 +0000

    make sure legacy var is always set

commit f41c85275d61f3a68dba6fc2e7aa3576ac032027
Author: Stan Hutcheon <stanhutcheon@bigfork.co.uk>
Date:   Thu Oct 30 11:24:14 2014 +0000

    Add correct action URL for pre 3.0

commit a0b4e6b26dd1d7b4a7d00ece5a781c96d0f54fe6
Author: Stan Hutcheon <stanhutcheon@bigfork.co.uk>
Date:   Thu Oct 30 11:21:35 2014 +0000

    more 2.4 stuffs

commit ac45e30c305661eeb06653827c3721cf5c585f76
Author: Stan Hutcheon <stanhutcheon@bigfork.co.uk>
Date:   Thu Oct 30 11:20:39 2014 +0000

    LeftAndMainExtension non existant in 2.4

commit 459acdc9c95f21e89baedd2c9cc9ecee3333ff2b
Author: Stan Hutcheon <stanhutcheon@bigfork.co.uk>
Date:   Thu Oct 30 11:16:50 2014 +0000

    experimental 2.4 support (untested)