vm_insnhelper.c: add comments

* vm_insnhelper.c (vm_yield_setup_block_args): break a long line and
  add comments.  remove useless code.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41019 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
vm_insnhelper.c: extract keyword arguments after splat

* vm_insnhelper.c (vm_yield_setup_block_args): split single parameter
  if any keyword arguments exist, and then extract keyword arguments.
  [ruby-core:55203] [Bug #8463]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41020 b2dd03c8-39d4-4d8f-98ff-823fe69b080e