[unwind-20030108-branch] Add sentinel-frame + misc

[Andrew Cagney]

> @@ -555,8 +522,14 @@
>>     If the value isn't here AND a value is needed, try the next inner
>>     most frame.  */
>>  
>> +struct frame_unwind_cache
>> +{
>> +  void *regs[1];
>> +};
>> +
> 
> 
> I know it makes some type-checking simpler, but naming all your private types
> the same thing is a real nuisance when using this lame "GDB" thing on
> the code afterwards.  Must we?

Looks like more bugs in gdb :-(

Andrew