vm.c: fetch retval iff necessary

	* vm.c (rb_vm_make_jump_tag_but_local_jump): get rid of fetching
	  retval when it is not used.  it is necessary for local jump
	  state only.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@62136 b2dd03c8-39d4-4d8f-98ff-823fe69b080e