Initial implementation of fast path operation for bitwise OR.

Initial implementation of fast path operation for bitwise OR.

Support a binary operation (bitwise OR) so long as it's not nested in
the left subexpression.  This ensures that the expression stack never
has height greater than two and so can be kept fully in registers.

The bounded expression stack height and the absence of any side
effects on the fast path allows us to still bailout out to the very
beginning of the function if any of our fast-path checks fail.

Review URL: http://codereview.chromium.org/594008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3822 ce2b1a6d-e550-0410-aec6-3dcde31c8c00