count DATA cells with stream ID 0 as delivered for SENDME purposes

Found while investigating 8093, but probably not the cause of it,
since this bug would result in us sending too few SENDMEs, not in us
receiving SENDMEs unexpectedly.

Bugfix on the fix for 7889, which has appeared in 0.2.4.10-alpha, but
not yet in any released 0.2.3.x version.
Check for orconns and use connection_or_close_for_error() when appropriate in connection_handle_write_impl()
Believe that v3 dirauths always serve extra infos.

Clients should always believe that v3 directory authorities serve
extra-info documents, regardless of whether their server descriptor
contains a "caches-extra-info" line or not.

Fixes part of #11683.
Turn --enable-buf-freelists off by default
Add --disable-mempools configure option
Forward-port 0.2.4.22 changelog
Document that we're incrementing version numbers in maint.

(ticket 9553)
Bump maint-0.2.4 version to 0.2.4.22-dev

(See discussion on #9553)
Merge remote-tracking branch 'origin/maint-0.2.4'

This is an "ours" merge, to avoid taking the commit that bumped
maint-0.2.4's version to 0.2.4.22-dev.
Turn --enable-mempools off by default
Add changes file for bug11476
note a comment that nickm didn't finish
Sandbox: allow access to stats/bridge-stats

Fix for 12041; bugfix on 0.2.5.1-alpha.
Fix a sentence that I never
Oops; permit rename with the correct filename
sandbox: Permit access to stats/dirreq-stats

This prevents a crash when rotating logs with dirreq-stats enabled

fixes 12035; bugfix on 0.2.5.1-alpha.
sandbox: Disallow options which would make us call exec()

None of the things we might exec() can possibly run under the
sanbox, so rather than crash later, we have to refuse to accept the
configuration nice and early.

The longer-term solution is to have an exec() helper, but wow is
that risky.

fixes 12043; bugfix on 0.2.5.1-alpha
sandbox: tolerate reloading with DirPortFrontPage set

Also, don't tolerate changing DirPortFrontPage.

Fixes bug 12028; bugfix on 0.2.5.1-alpha.
doc/HACKING: Improve documentation of how to bump version in maint

See discussion on 9553: Some of the build scripts don't like it when
you can't merge maint into release.
sandbox: support logfile rotation

Fixes bug 12032; bugfix on 0.2.5.1-alpha