Improve the branch and branch-trampoline mechanism to automatically
use long-jumps when function size grows large. Reduce size of emitted
trampoline pools.

Now passes mozilla regress-80981.js.

BUG=
TEST=

Review URL: http://codereview.chromium.org//7239020
Patch from Paul Lind <plind44@gmail.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8433 ce2b1a6d-e550-0410-aec6-3dcde31c8c00