Hello,

This patch adds frame sniffers (name stolen from other sniffer code) to 
the frame code.  Unlike the existing frame predicate methods that take a 
PC parameter, these take a full NEXT_FRAME.  It leaves the old frame 
predicates alone (making this safe for the branch).

I figure that should be enough to keep any unwinder, trying to decide if 
the frame is good, happy :-)

I'll look to commit this to both the trunk and 6.0 branch early next 
week.  I'll then follow up with patches to:

- rips out the old predicate methods (mainline only)

- replace the dwarf2 predicate with a dwarf2 sniffer
Will apply to mainline and branch.  Should fix weird edge case where a 
function has no cfi but is doing a tail call to a no-return function, 
but the code following the function does have CFI.

- (I guess) something to work around the dwarf2 unwind info (need to 
look at Mark's old code)

I've so far tested it on a RH9 system (with the sniffer enabled) and it 
hasn't shown a sign of regressing.

Can anyone point me at testcases that will magically start passing with 
this fixed?

Andrew