[Lightning] Tracked down some issues

[Francis McCabe]

I believe that I have tracked down the problem.

When you declare a jit_state variable locally, its initial state is undefined. 
When you declare it globally, it is initially full of zeroes.

The jit_patch_at macro tests the _jitl.long_jumps field. This field is never 
set as far as I can tell. 

There are references to jit_init(), but this macro is also not defined.

So, I hacked up one for my purposes, but I think it might be a good idea to 
define it properly.