prolog, pure guile scheme cont

[stefan]

Hey, 

I just read the code for prompts and aborts. 

So I had a problem with making prompts work effectivily due to the 
need to have two versions of a single prompt live at the same time
e.g. a Cut and the Next prompt that share the same tag. This does not
work if one reads the code. On the other hand defining a Cut tag prompt
and a Next tag prompt is not an elegant solution and is probably 
expensive. So, I'll turn over to c and will try to hack 
scm_at_abort and friends.

Have fun
/Stefan