OpenSystemsDevelopment / qpdf

* Add support for PCLm using setPCLm() and writePCLm() methods in
  QPDFWriter.hh and QPDFWriter.cc
* Add a function writePCLmHeader() for PCLm header in QPDFWriter

There is no need for a --precheck-streams option. We can do the
precheck without imposing any penalty, only re-encoding the stream if
it fails the first time.

This commit adds several API methods that enable control over which
types of filters QPDF will attempt to decode. It also adds support for
/RunLengthDecode and /DCTDecode filters for both encoding and
decoding.

Additional testing is added in later commits to be supported by
additional changes in the library.

Also accept more errors than before.

Eliminate PCRE and find endobj not preceded by endstream. Be more lax
about placement of endstream and endobj.

Preparing to refactor some pattern searching code to use these instead
of their own memchr loops. This should simplify the code that replaces
PCRE.

Sometimes we want to ignore bad tokens rather than having them throw
an exception. A coverage case is commented out here and added in a
later commit.

Also fix a bug resulting from incorrect use of PointerHolder because
of this unused parameter.

When parsing content streams, allow content to be split arbitrarily
across stream boundaries.

Be explicit about the need to keep the source QPDF object around.

When requested, QPDFWriter will do more aggress prechecking of streams
to make sure it can actually succeed in decoding them before
attempting to do so. This will allow preservation of raw data even
when the raw data is corrupted relative to the specified filters.

QPDFObjectHandle::parseInternal now issues warnings instead of
throwing exceptions for all error conditions that it finds (except
internal logic errors) and has stronger recovery for things like
invalid tokens and malformed dictionaries. This should improve qpdf's
ability to recover from a wide range of broken files that currently
cause it to fail.

During parsing of an object, sometimes parts of the object have to be
resolved. An example is stream lengths. If such an object directly or
indirectly points to the object being parsed, it can cause an infinite
loop. Guard against all cases of re-entrant resolution of objects.

This is CVE-2017-9209.

QPDFObjectHandle was used as forward declaration, but C++-Builder 10
Seattle can't use it in std::list in such cases because the type is
undefined.

Since we have to bump soname, remove some private methods that were
just there for binary compatibility

For non-encrypted files, determinstic ID generation uses file contents
instead of timestamp and file name. At a small runtime cost, this
enables generation of the same /ID if the same inputs are converted in
the same way multiple times.

QUtil.hh needs time.h to get time_t on some platforms. Thanks Peter
Korsgaard <peter@korsgaard.com>

Pushing inherited objects to pages and getting all pages were both
prone to stack overflow infinite loops if there were loops in the
Pages dictionary. There is a general weakness in the code in that any
part of the code that traverses the Pages structure would be prone to
this and would have to implement its own loop detection. A more robust
fix may provide some general method for handling the Pages structure,
but it's probably not worth doing.

Note: addition of *Internal2 private functions was done rather than
changing signatures of existing methods to avoid breaking
compatibility.

Add a method to get the current random data provider, and document and
test the method for resetting it.

Add new RandomDataProvider object and implement existing random number
generation in terms of that.  This enables end users to supply their
own random data providers.

If not available, give an error.  The user may also configure qpdf to
use an insecure random number generator.