freeze index site in BoundsCheckEvent::compile
freeze index site in BoundsCheckEvent::compile

This ensures we don't use it as a temporary register when generating
the comparison.

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