OpenSystemsDevelopment / qpdf

Add new convenience class QPDFObjGen::Guard

Also, change QPDFJob to use unique_ptr<QPDF> instead of shared pointers.

Now --json-output just changes defaults. Allow output file with --json.

* Replace --create-from-json=file with --json-input, which causes the
  regular input to be treated as json.
* Eliminate --to-json
* In --json=2, bring back "objects" and eliminate "objectinfo". Stream
  data is never present.
* In --json-output=2, write "qpdf-v2" with "objects" and include
  stream data.

Also add stubs for top-level QPDF methods (createFromJSON,
updateFromJSON)

moddify -> modify. Also carefully spell checked all remaining keys by
splitting them into words and running a spell checker, not just
relying on visual proofreading. That was the only one.

Update getJSON() methods and calls to them

This commit just changes the order in which fields are written to the
json without changing their content. All the json files in the test
suite were modified with this script to ensure that we didn't get any
changes other than ordering.

----------
#!/usr/bin/env python3
import json
import sys

def json_dumps(data):
    return json.dumps(data, ensure_ascii=False,
                      indent=2, separators=(',', ': '))

for filename in sys.argv[1:]:
    with open(filename, 'r') as f:
        data = json.loads(f.read())
    newdata = {}
    for i in ('version', 'parameters', 'pages', 'pagelabels',
              'acroform', 'attachments', 'encrypt', 'outlines',
              'objects', 'objectinfo'):
        if i in data:
            newdata[i] = data[i]
print(json_dumps(newdata))
----------

(patrepl and cleanpatch are my own utilities)

patrepl s/PointerHolder/std::shared_ptr/g {include,libqpdf}/qpdf/*.hh
patrepl s/PointerHolder/std::shared_ptr/g libqpdf/*.cc
patrepl s/make_pointer_holder/std::make_shared/g libqpdf/*.cc
patrepl s/make_array_pointer_holder/QUtil::make_shared_array/g libqpdf/*.cc
patrepl s,qpdf/std::shared_ptr,qpdf/PointerHolder, **/*.cc **/*.hh
git restore include/qpdf/PointerHolder.hh
cleanpatch
./format-code

Run this:

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

If we're opening a PDF file to copy its encryption information or
attachments, its version doesn't need to influence the output version.

Let argv be a null-terminated array. There is already code that
assumes this, and it makes it easier to construct the arguments.

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