[patch] Fix unwind handling for hppa

[Randolph Chung]

> In that only call the HP function when the generic one fails.  However, 
> first can you investigate the details?  This sort of thing needs to be 
> commented.

one more note about this:

skip_prologue_using_sal() sometimes returns a pc that is past the end of
a function. after_prologue() in hppa-tdep.c checks for this explicitly
and returns 0 in this case so that we can fall back to code reading.
this can be observed e.g. with gdb.base/break.exp with the
"breakpoint small function, optimized file" test. Is this expected? or
is it a bug in skip_prologue_using_sal()?

thanks,
randolph
-- 
Randolph Chung
Debian GNU/Linux Developer, hppa/ia64 ports
http://www.tausq.org/