OpenSystemsDevelopment / qpdf

Instead of directly putting the contents of the annotation appearance
streams into the page's content stream, add commands to render the
form xobjects directly. This is a more robust way to do it than the
original solution as it works properly with patterns and avoids
problems with resource name clashes between the pages and the form
xobjects.

Flatten annotations by integrating their appearance streams into the
content stream of the containing page. In the case of form fields,
only flatten if /NeedAppearance is false (or equivalently absent). If
flattening form fields, also remove /AcroForm from the document
catalog.

Generate page content fragment for rendering appearance streams
including all matrix calculation.

Unparse is admittedly strange, but I'd rather be strange and
consistent, and everything else in the qpdf library uses unparse to
serialize. (If you're reading this, the convention of using "unparse"
comes from the "clu" programming language.)

When @file is used and file doesn't exist, just treat it as a normal
argument.

The json mode implemented in this commit is not the final version, or
are the command line arguments used to invoke it.

Also move tests to libtests.

Now uses QPDFOutlineDocumentHelper and QPDFOutlineObjectHelper.