Hello,

The attached patch, moves the frame's type into `struct frame_unwind' 
and in doing so makes it possible to combine the sequence:

	prev->type = frame_type_from_pc()
	prev->unwind = frame_unwind_find_by_pc()

into a single:

	prev->unwind = frame_unwind_find_by_pc();
	// prev->type == prev->unwind->type;

and hence eliminate the the call to frame_type_from_pc().


Fine print:

While the above is true for new code, old code continues to use the same 
confused combination of frame_type_from_pc(), frame_unwind_find_by_pc(), 
deprecated_set_frame_type(), and legacy_get_prev_frame().  A legacy 
frame's type is initialized to UNKNOWN_FRAME, and then zero or more of 
those functions will override it.  get_frame_type() mapping an 
UNKNOWN_FRAME onto a NORMAL_FRAME.

Importantly, if a legacy frame's unwinder returns a known frame type 
(!UNKNOWN_FRAME) then that will be used in preference to any other 
value.  This should make it possible for old architectures to 
incrementally implement new unwinders.


Tested on d10v, ppc, and i386.  I'll commit in a few days,

Andrew