OpenSystemsDevelopment / qpdf

… shared helper retrieval, validation methods, and update usages across the codebase. Remove unused test coverage entries.

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.

Change .clang-format and commit automated changes from a fresh run of
format-code

Run this:

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

The executables that libtool built invoked the underlying binary with
an "lt-" prefix. The code contained numerous workarounds for testing,
which can now be removed.

Convert loop to use range-based for statement.
Remove unnecessary variables.

This comment expands all tabs using an 8-character tab-width. You
should ignore this commit when using git blame or use git blame -w.

In the early days, I used to use tabs where possible for indentation,
since emacs did this automatically. In recent years, I have switched
to only using spaces, which means qpdf source code has been a mixture
of spaces and tabs. I have avoided cleaning this up because of not
wanting gratuitous whitespaces change to cloud the output of git
blame, but I changed my mind after discussing with users who view qpdf
source code in editors/IDEs that have other tab widths by default and
in light of the fact that I am planning to start applying automatic
code formatting soon.

Expose Pl_QPDFTokenizer, and have it do more of the work of managing
the token filter's pipeline.