OpenSystemsDevelopment / qpdf

Apply various Clang-Tidy rules

Using search and replace.

Set indent differently for qdf and non-qdf files.
Combine with preceding newline for qdf files.

Also, uninitialize QPDFWriter::Members members.

Use string_view parameters and call pipeline write methods directly.

Move test for m->linearized outside loop.

I decided that it's actually fine to copy a direct object to another
QPDF. Even if we eventually prevent a QPDFObject from having multiple
parents, this could happen if an object is moved.

For consistency with similar methods, e.g. replaceObject.

Code tidy : replace 0 with nullptr or true

Remove any ambiguity around whether old or new value is being
returned.

Also, revert inlining of unparse and operator << from commit 4c6640c in
order to avoid exposing QUtil.

Remove variables obsoleted by commit 4f24617.