Include the loop header block when eliminating stack checks

Include the loop header block when eliminating stack checks

In simple unconditional loops - like the following - the hydrogen stack check elimination did not detect the call as the loop header block itself was not considered.

function f(o) {
  while(true) {
    o.a();
  }
}

R=fschneider@chromium.org

BUG=none
TEST=none

Review URL: http://codereview.chromium.org//7210010

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8329 ce2b1a6d-e550-0410-aec6-3dcde31c8c00