tumme and keyboard macros.

[Matt Hodges]

It might be useful for tumme-forward-char and tumme-backward-char
(perhaps tumme-{forward/backward}-image would be better names?) to
signal an error from the last and first thumbnails respectively.  This
would make useful `C-u 0 C-x e' type execution of keyboard macros in
*tumme* buffers.

(Support for prefix args would be good for all the movement commands.)

Thanks,

Matt