for an odd library mathn for the time being (only 1.9.x).
	  since grand mathn is must be very very special library for us.

	* rational.c: ditto.

	* ext/mathn/*/*: follow the above changes.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@20001 b2dd03c8-39d4-4d8f-98ff-823fe69b080e