Restore behavior of multiple .sp commands in HTML

Multiple .sp commands in HTML will now act like they do in text, and the
one with the largest value will be kept (rather than only the most recent
one). Ppgen used to work this way before 3.43, and we believe it should
still work that way for consistency.
3.43B: Fix typo in HTML doSpace routine
Fix problem with ellipses in .dt and with wrapping very short paragraphs

(1) ppgen temporarily transforms ellipses and some other special characters
into values that will not cause problems during processing, then it converts
them back into their real values near the end, just before writing the
output files. But for the .dt directive the reconversion at the end did not
occur, causing problems in the HTML title attribute.

(2) 3.42 had an error when wrapping very short "paragraphs" (one or two words)
that caused a Python exception.
3.43d Fix erroneous sc warning within .nf block

Normally ppgen will warn the PPer if it sees an all lower-case string of
text within sc /sc tags, as we never want all lower-case small-cap
strings. That case should be prepared by the formatters and the PPer
as all upper-case within the tags, instead.

However, for text within .nf blocks ppgen outputs each line in a div, and
so it needs to replicate any inline tags that span lines. This can result
in a line that is both all lower-case and within the sc tags, although the
complete string as prepared by the formatters and PPer was in fact
mixed-case. So, within a .nf block, ppgen will suppress that warning
message.
3.43e: Fix error in .di which generates incorrect HTML
Merge Develop 3.43e into Master; reset version to 3.44