Hello,

The attached patch cleans up the print_stack_frame interface vis:

- replaces ``level'' with ``print_level''
The old code was doing the ultimate dumness of:
	print_stack_frame (fi, frame_relative_level (fi), ...)
trusting that one matched the other ... :-/

- replaces ``int source'' with ``enum print_what print_what''
a very long standing cleanup

- replaces ``int args''  with the more meaningful ``int print_args''

An obvious follow-up is to merge print_args, print_level and print_what. 
  However, just getting this very long standing overhaul to work was 
hairy enough so I'm going to leave it for now.

Baring comments I'll commit it in a few days,
Andrew