API:
* Document::add_posting(): Fix bugs with the change in 1.4.8 to more
efficiently handle insertion of a batch of extra positions in ascending
order. These could lead to missing positions and corrupted encoded
positional data.
remote backend:
* Avoid hang if remote connection shutdown fails by not waiting for the
connection to close in this situation. Seems to fix occasional hangs seen on
macOS. Patch from Germán M. Bravo.