[Bug #1720] [NaN] == [NaN] が true になる

e$B%A%1%C%He(B #1720 e$B$,99?7$5$l$^$7$?!#e(B (by tadayoshi funaba)

e$B$=$s$J$KB.EYE*$K$-$D$$$s$G$9$+$M!#e(B
e$B$G$$l$P!$"$^$jL/$J$3$H$O$7$J$$$[$&$,$$$$$H;W$&$N$G!"e(B
e$B4{CN$NLdBj$H$7$FEvLL$Oe(B(4)e$B$H$9$k$H$+!#e(B

http://redmine.ruby-lang.org/issues/show/1720