configure.in: use PACKED_STRUCT_UNALIGNED on x64-mingw
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45171 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
configure.in: use PACKED_STRUCT_UNALIGNED on x64-mingw
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45171 b2dd03c8-39d4-4d8f-98ff-823fe69b080e