split assertions into algorithms

CentOS 7 seems finish MD5 support
http://chkbuild005.hsbt.org/chkbuild/ruby-trunk/log/20140722T140010Z.fail.html.gz

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46899 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-07-23

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46900 b2dd03c8-39d4-4d8f-98ff-823fe69b080e