Hello,

I have attached a patch that implements tail-call elimination for a subset
of emacs lisp.  This will be helpful in allowing coding styles which
emphasize tail recursion, such as is usual in languages like Scheme.
The subset of emacs lisp that is targeted is compiled and lexically bound.

There are some downsides to tail-call elimination.  The most obvious is
that debugging will be more complicated.  Since the memory usage is not
allowed to grow because of a tail call, the debug stack will not show the
function that was called in the tail call.  I think the benefits outweigh
this, but I'm obviously biased. :)

I'm also not a regular contributor to emacs, so please let me know if there
is anything I need to do to the patch to get it accepted.

Cheers,
Chris