merge revision(s) r45845,r45846,r45847: [Backport #9486]

	* parse.y (local_tbl_gen): remove local variables duplicated with
	  arguments.

	* parse.y (new_bv_gen): no duplicated names, if already added in
	  shadowing_lvar().
	  [ruby-core:60501] [Bug #9486]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@46596 b2dd03c8-39d4-4d8f-98ff-823fe69b080e