[xml] Added new child to DOM tree does not have line breaks.

["Debin Chen" <debinc promise com>]

Hi, Daniel 

I had a problem when saving a edited DOM tree to XML file using
xmlSaveFormatFileEnc(). If I use the example provided by tree2.c, it is
perfect, because the DOM tree is created from scratch, then a few
children added. 

However, if I edit a DOM tree by opening an existing XMl file, then
added a few children. After I save it, the problem is that the newly
added children works, but they do not have line breaks. One line holds
all the children and it is of course hard to read when editing the file
again.

Is there already such bug or it is fixed? I am using 2.6.4.

Thank you for your hard work and continuous support for libxml2.

Regards.

Debin