fix deleting an image anchored to last paragraph in document

It only compared nodes instead of SwPositions, thus refusing to delete
anything anchored at the last content node. Also, select-all makes
rEnd point to the last content node, after its content. So if
an anchor-to-char image is anchored at the end of the paragraph,
it points to this place, too, so that must be checked.

Change-Id: Ie0ba6ed59f47e59492ad88577392884cadb52106
show fly anchored inside selection as selected too

If part (or whole) document is selected and then the selection
is e.g. deleted, flys anchored there will be deleted too, so it
makes sense to show them as part of the selection.

Change-Id: I17bfccebc0cd305c19616159471f0f113c7e71d9