The hydrogen stack check instruction is now added to each loop and the stack check handling on the back edge has been removed.

This change causes regression on small tight loops as the stack check is now at the top of the loop instead of at the bottom, and that requires one additional unconditional jump per loop iteration. However the reason for this change is to avoid worse regressions for upcoming changes to correctly support debugger break in optimized code.

R=fschneider@chromium.org

BUG=none
TEST=none

Review URL: http://codereview.chromium.org//7216009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8428 ce2b1a6d-e550-0410-aec6-3dcde31c8c00