[Ruby 1.9-Bug#3490] test_pack_utf8 failure on mswin64

[Yui_NARUSE]

e$B%A%1%C%He(B #3490 e$B$,99?7$5$l$^$7$?!#e(B (by Yui NARUSE)

e$BM%@hEYe(B Lowe$B$+$ie(BNormale$B$KJQ99e(B
Target version 1.9.2e$B$+$ie(B1.9.3e$B$KJQ99e(B

e$BK:$l5n$i$l$F$$$k5$$,$9$k$N$G!"0lEYM%@hEY$r>e$2$^$9e(B

http://redmine.ruby-lang.org/issues/show/3490