Problems with TranscodeToStr

This is actually 3 reports in one (but hey, sue me

1. TranscodeToStr fails of the XMLCh-string contains just one character when encoding is "WCHAR_T" or "UTF-32" (i.e. types larger than XMLCh) and you get "invalid-multibyte-character"

2. In the constructor of TranscodeToStr, the result (or 'failReason') from makeNewTranscoderFrom is never checked and if it fails the ::transcode-function dumps miserably. An exception would be preffered

3. It is not documented why the parameter 'manager' is not used (in the call to makeNewTranscoderFrom instead and not to the ::transcode-function) but the (global) fMemoryManager is used instead