common.mk: Created new target update-unicode to download
	   some Unicode data files.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47723 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-09-28

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47724 b2dd03c8-39d4-4d8f-98ff-823fe69b080e