Handle PTD_FOR_INCLUSION properly

Change handling of PTD_FOR_INCLUSION to match that of the parser (i.e.,
don't set it if text is being expanded in the root frame), so that
frame:getParent():preprocess() will handle <noinclude> etc. correctly.

Change-Id: I13f45e57aa334642d310e9bd5fdd3dbe5922c4e1
Merge "Handle PTD_FOR_INCLUSION properly"