Implemented xxxComment. Due to different minidom XML types (Comments

Implemented xxxComment. Due to different minidom XML types (Comments
are not Elements) had to add xxxObject.isElement flag and changed
xxxObject.element variable to xxxObject.node (xxxComment is derived
from xxxObject to minimize changes in processing). More testing is still
needed to verify that things didn't break. Use previous commit (0.1.8-4
release on 2007/03/10) if you need a stable version.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@44764 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775