Reverted r11835 'Unify promotion and allocation limit computation' due to V8 Splay performance regression on Mac.  (Chromium issue 134183)

Fixed sharing of literal boilerplates for optimized code.  (issue 2193)

Performance and stability improvements on all platforms.

git-svn-id: http://v8.googlecode.com/svn/trunk@11918 ce2b1a6d-e550-0410-aec6-3dcde31c8c00