Temporarily replace .get invocations with direct .buffer accesses.

Replacement inspired after shu noted ~10x improvement with that
change.  See discussion here: http://logbot.glob.com.au/?c=mozilla%23pjs#c16318
Made wavefront calculation sequential.
Checkpoint state though I am not sure of status.
Add standard JS array variant to liquid-resize demo.

Adding standard JS array variant in order to sanity check comparisons
against sequential code using image buffers.

(Answer: using an image buffer is 10x faster, at least with this port.
May be good to check with typed arrays and maybe also with a version
that uses untyped arrays but doesn't put non-index properties on the
array objects.)
Improve performance of seq pure JS array version by using 1 array entry per pixel.

The earlier version was using 4 array entries per pixel (4x space blowup).
This change yields about a 2.3x speedup.
Checkpoint state while I track down bug in code.
Implemented Typed Array variant (it was just a skeletal clone before).

Note that if one is going to have the objects carry properties like
'width' and 'height', then you need to put them on the backing
ArrayBuffer (and not the Uint8Array views), due to:

  Bug 695438 - TypedArrays don't support new named properties
  https://bugzilla.mozilla.org/show_bug.cgi?id=695438