[PATCH] Let dwarf2 CFI's execute_stack_op be used outside of CFI

[Daniel Berlin]

So i'm implementing this, and want to know
...
> /* Return the value N values down from the top of CONTEXT's stack.
>    This raises an error if there aren't at least N+1 values on the stack.  */
> ADDR_TYPE dwarf_expr_fetch (struct dwarf_expr_context *context, int n);
> 

How would you like me to raise the error?
Should i add an error handling function to the dwarf_expr_context struct? 
Or just call "error", under the assumption that any libdwarf library we 
write would have error functions of it's own (all the libdwarf's do), and 
that it'll be the typical printf arguments error function.

--Dan