Improve instruction creating/adding shorthand in HGraphBuilder

Add multi-argument templates for New, NewUncasted, Add and AddUncasted that
call boilerplate HInstruction::New methods rather than the constructor directly.
This allows for automatic passing of the zone and context for instructions that
need them.

R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/21356002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15990 ce2b1a6d-e550-0410-aec6-3dcde31c8c00