Hello,

Attached are two tweaks to the PPC skip_prologue method so that it works 
better with glibc:

- handle glibc syscall
Without this an unwinder won't be able to find its way out of a system 
call - it needs to figure out the location of a local label, see comment 
for details.

- handle PIC code where the LR appears to be saved twice
It appears that skip_prologue code tried to handle this but missed an 
edge case.  Without this the wrong LR gets used when trying to unwind 
out of GLIBC.

Ok for mainline?

Andrew