Remove unused JsonML support from JS parse trees.

Context:
<https://groups.google.com/d/topic/google-caja-discuss/RCHSAbB1-Zs/discussion>

@r5669

[felix8a, 2014-02-24 22:27:55]

jsonml.jar removal isn't in the CL
otherwise LGTM

[kpreid2, 2014-02-24 22:37:56]

On 2014/02/24 22:27:55, felix8a wrote:
> jsonml.jar removal isn't in the CL
> otherwise LGTM

Oops, forgot to propetly sync that deletion. Done.
@r5669

[felix8a, 2014-02-24 23:53:40]

please also backport to es53

[kpreid2, 2014-02-25 00:09:57]

On 2014/02/24 23:53:40, felix8a wrote:
> please also backport to es53

I backport things no more than once a week, in order to reduce the noise of
extra commits. Is there a reason to do them individually?

[felix8a, 2014-02-25 00:12:31]

On 2014/02/25 00:09:57, kpreid2 wrote:
> On 2014/02/24 23:53:40, felix8a wrote:
> > please also backport to es53
> 
> I backport things no more than once a week, in order to reduce the noise of
> extra commits. Is there a reason to do them individually?

either way is fine by me. I tend to commit to both trunk and es53 at the same
time since I have all the knowledge of the change fresh in my head, and then I
can forget about it.