merge revision(s) r45360,r45361: [Backport #9651]

	* vm_eval.c (eval_string_with_cref): Use file path even if scope is
	  given. Related to [ruby-core:56099] [Bug #8662] and r42103.

	* vm_eval.c (eval_string_with_cref): Unify to use NIL_P.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@45474 b2dd03c8-39d4-4d8f-98ff-823fe69b080e