[Bug #1957] NKF.nkf でシフトJISの "\e" が "" に変換される

e$B%A%1%C%He(B #1957 e$B$,99?7$5$l$^$7$?!#e(B (by Yui NARUSE)

e$B8=>u<N$F$F$$$^$9$M!#e(B
e$B;D$7$F$*$$$?J}$,$$$$$G$9$+e(B?
e$B$^$?!"$3$NJQ99$Oe(B1.8.7e$B$N%Q%C%A%j%j!<%9$K$b4^$a$?$$$G$9$+e(B?

http://redmine.ruby-lang.org/issues/show/1957