* doc, docx: keep the compound border lines
The nine thin and thick compound lines (thinThickSmallGap to thinThickThinLargeGap, ECMA-376 17.18.2)
were read as a single line and written back as one, on paragraphs, tables, cells and pages. BorderStyle
gains them; they are written back by name and drawn as a single line of the border's width, as before.
RTF export and import carry them too (the importer read four of them as double).
* contributors: add entropybeater
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Co-authored-by: Brian <255903314+entropybeater@users.noreply.github.com>