OpenSystemsDevelopment / qpdf

…ternal2 and copyObject2

copyObject2 repeats a second time what
new_obj = QPDFObjectHandle(obj->copy(true))
in shallowCopyInternal2 already did.

…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.

Avoid representing as PDF Doc encoding any string whose PDF Doc
encoding representation starts with a UTF-16 or UTF-8 marker.

Base implementation of the buffer on std::basic_string<unsigned char>.

An indirect object reference to 0, 0 is invalid. If it appears in the
file or is parsed from a string, the parser catches it. This check
would only be useful for someone explicitly calling getObject with 0,
0, and that would trigger an error during resolve().