codeintel: be able to switch doctypes for an existing buffer
http://bugs.activestate.com/show_bug.cgi?id=100250

Note that namespace currently override doctype choices.

(integrated from komodo (trunk) change 82136 by marky)

git-svn-id: http://svn.openkomodo.com/repos/openkomodo/trunk@13673 b87d16e7-d29f-4ee1-b5ec-817d645d335f