saveIncremental

Produce the updated document bytes: original + appended objects + new xref section + trailer. When nothing was staged or overridden this is a verbatim copy of the original.

When the document opened through repair, its own table is the broken part, so the appended table stands alone: it lists every object at the offset repair found and names no /Prev, and the objects that lived inside an object stream, which a classic table cannot point into, are written out again (#586).