OpenSystemsDevelopment / qpdf

Allowing users to subclass InputSource and Pipeline to read and write
from/to arbitrary sources provides the maximum flexibility for users
who want to read and write from other than files or memory.

This makes it possible to use two different writers to write
linearized files from the same QPDF object.

Previously only whitespace and comments did it.  This fix is needed
for object streams whose last object is a literal (name, integer,
real, string) not terminated by space or newline.

Previous commit lost coverage case for buffer-based replaceStreamData.

Implement --pages ... -- option for qpdf.  Update TODO with remaining
things to document.

Move object parsing code from QPDF to QPDFObjectHandle and
parameterize the parts of it that are specific to a QPDF object.
Provide a version that can't handle indirect objects and that can be
called on an arbitrary string.

A side effect of this change is that the offset used when reporting
invalid stream length has changed, but since the new value seems like
a better value than the old one, the test suite has been updated
rather than making the code backward compatible.  This only effects
the offset reported for invalid streams that lack /Length or have an
invalid /Length key.

Updated some test code and exmaples to use QPDFObjectHandle::parse.

Supporting changes include adding a BufferInputSource constructor that
takes a string.

Add --copy-encryption and --encryption-file-password options to qpdf.
Also strengthen test suite for copying encryption.  The strengthened
test suite would have caught the failure to preserve AES and the
failure to update the file version, which was invalidating the
encrypted data.

Method to copy encryption parameters from another file.  Adapted from
existing code to copy encryption parameters from the original file.

Throw an exception that directs the user to QPDF::copyForeignObject.

This includes QPDF::copyForeignObject and supporting foreign objects
as arguments to addPage*.

QPDFObjectHandle::{new,is,assert}Reserved, QPDF::replaceReserved
provide a mechanism to add objects to a PDF file when there are
circular references.  This is a prerequisite to copying objects from
one PDF to another.

Breaking API change: length parameter has disappeared from the
StreamDataProvider version of QPDFObjectHandle::replaceStreamData
since it is no longer necessary to compute it in advance.  This
breaking change is justified by the fact that removing the length
parameter provides the caller an opportunity to simplify the calling
code.

Also updated pdf_from_scratch test driver to use the new factories,
and made some cosmetic improvements and documentation updates for the
emptyPDF() method.

Place user-specified CPPFLAGS and LDFLAGS later so that user-specified
non-standard paths that have old versions of qpdf don't cause the
build to fail.

off_t is used internally only when needed to talk to standard
libraries.  This requires that the "long long" type be supported by
the compiler.