OpenSystemsDevelopment / qpdf

Pandoc doesn't convert <xref> correctly, but it does so consistently,
so this commit just changes all xref links to :ref:.

At one time, it seems that I was starting to use the <firstterm>
feature of docbook, but I forgot about it long ago, and there is
nothing consistent. In the absence of an actual glossary, just use
emphasis for terminology and don't tag it in any special way. This
could be fixed later if we wanted to.

All occurrences are in :file: or :samp: now.

Replace @1@replaceable@1@...@2@replaceable@2@ with
@3@replaceable@3@...@3@replaceable@3@ inside of :samp: and :file: so
that all remaining @1@replaceable@1@...@2@replaceable@2@ are outside.
Since the {...} syntax for replaceable only works in :samp: and
:file:, we will have to enclose the remaining ones in :samp: for them
to work.

:option: is stronger and assumes a reference to a list of options.
Since we don't have that yet, just use :samp: for options. Inside
literal code blocks, there is no expansion, so just remove markup.

Replace @1@...@2@ stuff from prior to the conversion with new
representation.

Pandoc indented lists with two spaces after the dash, which is ugly
and messes up emacs fill-paragraph. I transformed the spacing using a
combination of this perl script and manual edits. I verified that the
HTML generated by sphinx was identical before and after the edits and
that this commit contains only whitespace changes. The perl script as
it stands does not do indentation quite right for variable lists, but
there were only about 8 cases that it missed, so I just fixed them
manually.

```perl
#!/usr/bin/env perl
require 5.008;
use warnings;
use strict;
use File::Basename;

my $whoami = basename($0);

my @liststack = ();

while (<>)
{
    if (m/^( *-  )\S/)
    {
        my $pre = $1;
        while ((scalar(@liststack) > 0) &&
               ($liststack[-1] >= length($pre)))
        {
            pop(@liststack);
        }
        if ((scalar(@liststack) == 0) && ($pre =~ m/^ /))
        {
            push(@liststack, 1);
        }
        push(@liststack, length($pre));
        my $n = scalar(@liststack);
        #print "** $n\n";
        my $newpre = ('  ' x ($n - 1)) . '- ';
        s/^$pre/$newpre/;
    }
    elsif (scalar(@liststack) > 0)
    {
        if ($_ ne "\n")
        {
            while (scalar(@liststack) > 0)
            {
                my $pre = m/^( *)/;
                if (length($1) < $liststack[-1])
                {
                    #print "XXX pop\n";
                    pop(@liststack);
                }
                else
                {
                    last;
                }
            }
            my $n = scalar(@liststack);
            #print "** $n\n";
            my $indent = '  ' x $n;
            s/^ +/$indent/;
        }
    }
    print;
}
```

These showed up as warnings from sphinx-build

Also remove linearization from qpdf-manual.pdf. It's a small file, and
removing the dependency on the qpdf executable significantly shortens
build times.

pandoc -f docbook -t rst qpdf-manual.xml >| /tmp/a.rst
Insert /tmp/a.rst into existing index.rst

Run sphinx-quickstart. Throw everything away except conf.py and
index.rst. We will incorporate this into our own build system.

We were using SGML entities for various non-ASCII characters so they
could convert properly for both HTML and print, but this is no longer
necessary as we move from docbook to RST, so just replace them. Note
that the conversions done by sphinx automatically handle "smart
quotes", so it works to just use regular quotes in place of “
and ”.

Pandoc docbook -> rst fails to convert the following elements, so
change them to @1@tag@1@ ... @2@tag@2@ for later processing. This way,
they will survive the conversion, and we can deal with them later.

<application>
<command>
<filename>
<firstterm>
<option>
<replaceable>

With docbook, this was not converted properly in the PDF version, but
since we are moving out of docbook, we can just put the Unicode
character in the source.

Footnotes are yucky in online documentation, and the one footnote in
the doc is no longer needed, so remove it.

Make a list of things that need to be done while converting docbook to
sphinx/rst.

* Make it a runtime error, not a logic error
* Include additional information
* Capture it properly in checkLinearization

* Handle error conditions that occur when using the object handle
  interfaces. In the past, some exceptions were not correctly
  converted to errors or warnings.
* Add more detailed information to qpdf-c.h
* Make it possible to work more explicitly with uninitialized objects

It was exercised in the pdf-linearize example but not in qpdf-ctest.

Thanks for the nudge from m-holger!

The impact on the code would be extremely high, and using it would
clutter the code greatly because it would break chaining like
a.getKey("/B").getKey("/C"). There are better ways to deal with the
issue.