This more or less restores the original custom layout where the TOC is
on the right side, with a CSS workaround added for portrait orientation.
The indentation of sub-lists in the TOC has been decreased.
The sizes of HTML headings and the "h0" div generated for each Doxygen
page have been adjusted to look better together now that they can meet.
A few headings have been shortened to fit better in the narrower TOC.