Follow-up to #225. The session still waits 30 minutes in all for a map
(checking, the two-minute question, download, install, apply, join), and
servers and lobbies still let a player go at 30 minutes. But a download
that has begun is no longer cut off at 27 minutes: a large map on a slow
connection never came at all that way.
- Once the download has begun, the session's deadline is the session's
alone. The download goes on (up to its own four hours, as before #225),
installs and is applied, and the player is told to join again; no
rejoin is tried past the deadline, where the server would turn them
away. "Map still downloading" says so when the session stops waiting.
- Before the download, the deadline still ends the check and the question.
Declining or cancelling still stops it and removes the partial file.
- A download whose session has gone is not cancelled by joining another
session; a new map need is turned away until it is done.
- The 27-minute transfer budget and its completion reserve are gone from
map_fetch_policy.h, with their tests; the map download tests cover the
new behaviour.
- The HTTPS timeout test compiles with warnings as errors (a signed and
unsigned comparison), and get_text's stale-file removal is indented again.
- README: map downloads described as they now are.