This change makes the number of successors of a control instruction
configurable with a template parameter and changes the existing instructions
to use it.

To iterate over all successors I added an iterator instead of always calling
First- and SecondSuccessor.
Review URL: http://codereview.chromium.org/7114004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8262 ce2b1a6d-e550-0410-aec6-3dcde31c8c00