[xml] Bug in UTF8ToUTF16LE?

[Stuart Dootson <stuart dootson gmail com>]

The specification for xmlCharEncodingOutputFunc says that the function
will return 'the number of bytes written, -1 if lack of space, or -2
if the transcoding failed'. UTF8ToUTF16LE (which is the implementation
of that interface for the UTF16LE encoding) appears to return 0 on
success (appears to be confirmed by an examination of the 2.6.13
source code).

Having said that, several (I didn't check them all) of the converter
functions look like they return 0 on success - is it the documentation
that's incorrect?