OpenSystemsDevelopment / qpdf

PointerHolder will be replaced with shared_ptr, so let people start
moving.

Replace most of the calls to QUtil::copy_string with this instead.

* Make it a runtime error, not a logic error
* Include additional information
* Capture it properly in checkLinearization

* Handle error conditions that occur when using the object handle
  interfaces. In the past, some exceptions were not correctly
  converted to errors or warnings.
* Add more detailed information to qpdf-c.h
* Make it possible to work more explicitly with uninitialized objects

Don't assume endobj is at the beginning of the line. This means we are
looking at tokens for every line, but the odds of n n obj appearing in
the middle of the object are likely much lower than endobj not being
at the beginning of the line or missing entirely. This will probably
have a negative impact on recovery time for very large files.
Hopefully it will be worth it.