Wrongful conversion of utf8-characters

[martin.s...@gmail.com]

It seems that uglify v1 (don't know about v2, haven't tested it) will encode UTF characters even those between \uD800 and \uDFFF, the things is, these characters don't exist and shouldn't be translated. 

And it seems to cause some issues in the later Chrome release where the converted symbol is read by the javascript engine.