OpenSystemsDevelopment / qpdf

…ternal2 and copyObject2

Have separate versions for unsafeShallowCopy, shallowCopy and makeDirect.

Add optional parameter shallow. Change logic errors to runtime errors.

Lazily load MD5 and RC4 once in the life of the program. Only load the
legacy provider if RC4 is actually being used.

* Define it even though previous experiments have shown it to be
  unnecessary since it seems like it may be necessary after all
* Add QPDF_DLL_CLASS to QPDFObjectHelper and QPDFDocumentHelper in
  case there's some future unknown reason why someone may want to have
  them and/or in case it helps with the weird
  QPDFNameTreeObjectHelper problem.

It has disappeared from the DLL on Windows a few times.

That way we can always ensure that the right compiler flags are being
used if there is an issue.

Verify runpath for all executables, check to make sure the AppImage
works in various intended ways.

* Use correct cmake flag to not build static libraries
* Force correct relative RPATH in installed executables