Invalid XML characters handling in Util.toXML() and XMLEncoder

[Former user]

Original issue 258 created by @ysavourel on 2012-07-26T13:02:18.000Z:

Need to auto-change invalid XML chars to something like _#xHHHH; in Util.toXML() and the XMLEncoder.
this is to resolve once for all the recurring problem with files having bad characters.

[Former user]

Comment 1. originally posted by @ysavourel on 2014-02-27T17:19:25.000Z:

Decission was to shift by 0xF000 the control characters invalid in XML.
In XLIFFWriter, TMXWriter, possible XLIFFWriter. / encoders?
We should also have an isValidXMLCharacter() helper method.

[Jim Hargrave (OLD)]

This appears to still be an issue and needs to be fixed