OpenSystemsDevelopment / qpdf

This change updates all occurrences of `std::endl` to `\n` across various files for improved efficiency and consistency. It reduces unnecessary flushing of output buffers associated with `std::endl` while maintaining the same output format.

Prevent my future self or other contributors from using assert in
tests and then having that assert not do anything because of the
NDEBUG macro.

Run this:

for i in  **/*.cc **/*.c **/*.h **/*.hh; do
  clang-format < $i >| $i.new && mv $i.new $i
done

This makes it much more convention to use the initializeFromArgv
functions since you can use string literals.

This was used, but it no longer is, so let's not keep the extra
complexity around.

Handle optional choices in addition to required choices. Refactor the
way help options are added to completion to make it work with optional
help choices.