OpenSystemsDevelopment / qpdf

Most of the README files have been renamed. Refer to the new names.

Slightly improve memory cleanup in Pl_DCT
Make it easier to test with valgrind

While scanning the file looking for objects, limit the length of
tokens we allow. This prevents us from getting caught up in reading a
file character by character while digging through large streams.

A stray semicolon caused a condition to be incorrectly applied during
stream length recovery.

Pushing member variables into a nested class enables addition of new
member variables without breaking binary compatibility.

Reduce code duplication

Files written in PCLm mode have to be created in a very specific way.
qpdf doesn't know how to create PCLm files from scratch. All it knows
how to do is to write an already valid file in a suitable way.
Therefore there is no command-line support for PCLm.

Remove duplicated coverage cases from Sahil's code so existing test
suite passes.

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

Replace the old msys, mingw-w64, ActiveState perl setup with MSYS2.
This greatly simplifies the Windows build. This was facilitated by the
need to incorporate JPEG.

pdf-create now creates images with different color spaces and encoding
schemes and verifies them for data correctness.

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.

There was an unintended recoverable error in a test file. It wasn't
hurting anything, but it was obscuring the actual intent of the test.

This reverts commit 8ee83ca722baad9434119bb72d620dfd8e6103c4.

This is being removed because qpdf now has its own page rotation. The
example was an excellent contribution to qpdf, but now it illustrates
rotating pages "by hand", which is no longer needed because of
QPDFObjectHandle::rotatePage.