[Backport #1656](Assigned) fdiv の使用で Segmentation fault が発生する

e$B%A%1%C%He(B #1656 e$B$,99?7$5$l$^$7$?!#e(B (by Nobuyoshi N.)

e$B%9%F!<%?%9e(B Opene$B$+$ie(BAssignede$B$KJQ99e(B
e$BC4Ev<Te(B Shyouhei U.e$B$K%;%C%He(B

fixed at r23740.

http://redmine.ruby-lang.org/issues/show/1656