Hello,

This, finally, is the tweak to the dwarf2-unwind code, to use the 
frame's address-in-block, instead of the frame's PC to select the CFI 
info.  Two test cases stop failing:

1gdb.base/corefile.exp: backtrace in corefile.exp FAIL PASS 
2gdb.base/gdb1250.exp: backtrace from abort KFAIL PASS

Ok for the mainline?
Ok to pull something equivalent into 6.0 branch?

Andrew