[REVIEW 3-5] fdo#49342 crash in cell merge of "old-school" tables

[Caolán McNamara]

This is a revert of 858b5b4f36a357fe7192e7c2ed9cc3cdfc81fd8f and some
related follow up fixes to convert SwSelBoxes to a std::map from a
SV_DECL_PTRARR_SORT

The std::map uses SwTableBox::GetSttIdx as a key, which looked like a
good idea, but digging into fdo#49342 there are a number of scenarios
where content gets added to the document after the Boxes are shoved into
a SwSelBoxes but before the SwSelBox is used. Which means the nodes get
moved so their GetSttIdx returns a different value, but the std::map's
key is a stale copy of the GetSttIdx, so it can't find them by their new
keys. Onwards to epic fails :-(

Suggest the attached revert for 3-5, which I'll try and massage into
master as well. A sorted std::vector looks like the best fit. rather
than a std::map, to keep the current tangled logic working post stl
conversion.

C.

this might be the reason behind the other rtf table crash mentioned
earlier, I've yet to dig out the bug no for that to re-test.