OpenSystemsDevelopment / qpdf

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.

Update the build to support new external-libs layout, and autoconf
options to specify windows word size.  Split make_windows_releases
into multiple scripts.

Thanks Tobias Hoffmann for noticing the error.

Split optimizePagesTree into a simpler top-level routine and a
recursive internal routine.

The method is helpful in other places, like the upcoming QPDF::addPage, too.

Added methods to append to arrays, insert items into arrays, and
replace array contents with a vector of items.

Significantly improve the code's use of off_t for file offsets, size_t
for memory sizes, and integer types in cases where there has to be
compatibility with external interfaces.  Rework sections of the code
that would have prevented qpdf from working on files larger than 2 (or
maybe 4) GB in size.

New header qpdf/Types.h attempts to make sure size_t and off_t are
defined on any platform and in a way that would work with large file
support.  Additionally, missing header files are included to get
unlink.

For ELF systems, turn on versioned symbols by default, and add a
configure option to enable or disable them.