Set the prefix string that appears before error messages issued by Berkeley DB.
The DB->set_errpfx function does not copy the memory referenced by the
errpfx argument, rather, it maintains a reference to it. This
allows applications to modify the error message prefix at any time,
without repeatedly calling DB->set_errpfx, but means that the
memory must be maintained until the handle is closed.
For DB handles opened inside of Berkeley DB environments, calling the
DB->set_errpfx function affects the entire environment and is equivalent to calling
the DBENV->set_errpfx function.
The DB->set_errpfx interface may be used to configure Berkeley DB at any time
during the life of the application.