fix instruction offset calculation in powerpc.cpp
fix instruction offset calculation in powerpc.cpp

The previous code did not take into account any padding embedded in a
basic block due to inline jump tables, which led to invalid code
generation in large methods

ucdseniordesign/avian,bigfatbrowncat/avian-pack.avian,lwahlmeier/avian,marcinolawski/avian,bgould/avian,getlantern/avian,badlogic/avian,lostdj/avian,lostdj/avian,badlogic/avian,dicej/avian,getlantern/avian,getlantern/avian,joshuawarner32/avian,marcinolawski/avian,lwahlmeier/avian,ucdseniordesign/avian,bgould/avian,dicej/avian,lostdj/avian,lwahlmeier/avian,joshuawarner32/avian,MaartenR/avian,dicej/avian,minor-jason/avian,joshuawarner32/avian,lwahlmeier/avian,bigfatbrowncat/avian-pack.avian,bgould/avian,lostdj/avian,ucdseniordesign/avian,getlantern/avian,minor-jason/avian,joshuawarner32/avian,bigfatbrowncat/avian-pack.avian,bgould/avian,MaartenR/avian,marcinolawski/avian,minor-jason/avian,ucdseniordesign/avian,bigfatbrowncat/avian-pack.avian,badlogic/avian,MaartenR/avian,minor-jason/avian,badlogic/avian,dicej/avian,marcinolawski/avian,MaartenR/avian