* vm_exec.h: declare two macros
  * START_OF_ORIGINAL_INSN()
  * DISPATCH_ORIGINAL_INSN()
  instead of inserting label and goto lines.
  For OPT_CALL_THREADED_CODE, first macro is empty and second macro
  is simply call the original insn function.

* tool/instruction.rb: use above macros.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61120 b2dd03c8-39d4-4d8f-98ff-823fe69b080e