OpenSystemsDevelopment / qpdf

They have to be ot_* rather than qpdf_ot_* for compatibility.

* Different enumerated types are not assignment-compatible in C++, at
  least with strict compiler settings
* While you can do `constexpr ot_xyz = ::qpdf_ot_xyz` in QPDFObject.hh to
  make QPDFObject::ot_xyz work, QPDFObject::object_type_e::ot_xyz will
  only work if the enumerated type names are the same.

Too bad about git annotate but it was pretty crazy to have all those
test cases together like that.

QPDFObjectHandle gets copied a lot, so let's not add another field.
For performance reasons, QPDFObjectHandle does not indirect through a
smart pointer, so this would also be an ABI change.

The agogo theme doesn't do very well on narrow screens. The code
blocks were used for shell commands but were using Python syntax
highlighting.