Fixes bug 31374; bugfix on 0.2.9.1-alpha.

My previous fix removed a comparison, which would have caused us to
warn about every skew instead of skews of over an hour.

On some windows builds, time_t is 64 bits but long is not.  This is
causing appveyor builds to fail.

Also, one of our uses of labs() on time_t was logically incorrect:
it was telling us to accept NETINFO cells up to three minutes
_before_ the message they were responding to, which doesn't make
sense.

This patch adds a time_abs() function that we should eventually move
to intmath.h or something.  For now, though, it will make merges
easier to have it file-local in channeltls.c.

Fixes bug 31343; bugfix on 0.2.4.4-alpha.

Linux is the first item in the os matrix, so we don't need to specify
it under matrix: include: .

Part of 29280.

Part of 29280.

Part of 29280.

Replace the 157 fallbacks originally introduced in Tor 0.3.5.6-rc
in December 2018 (of which ~122 were still functional), with a
list of 148 fallbacks (70 new, 78 existing, 79 removed) generated
in June 2019.

Closes ticket 28795.

Note that we created extra lists from DE and US, but they didn't add
any more fallbacks when we tried to merge them.

Update the fallback directory mirrors by merging the current list with:
fallback_dirs_2019-06-28-08-58-39_AU_f0437a39ddbc8459.inc

Part of 28795, see that ticket for logs.

Update the fallback directory mirrors by replacing the old list with:
fallback_dirs_2019-06-25-11-49-10_AU_a37adb956fbb5cd2.inc

Part of 28795, see that ticket for logs.

Previously we had "make check" launched whenever DISTCHECK was
false.  Now we'd like to turn it off in a few other circumstances,
like running chutney.  Maybe stem too?

See: https://blog.travis-ci.com/2018-11-19-required-linux-infrastructure-migration

We need to keep the gcno files, because they are created at compile time.

When classifying a client's selection of TLS ciphers, if the client
ciphers are not yet available, do not cache the result. Previously,
we had cached the unavailability of the cipher list and never looked
again, which in turn led us to assume that the client only supported
the ancient V1 link protocol.  This, in turn, was causing Stem
integration tests to stall in some cases.  Fixes bug 30021; bugfix
on 0.2.4.8-alpha.

And fix a comment.

See:
https://gcc.gnu.org/onlinedocs/gcc/Gcov-Data-Files.html#Gcov-Data-Files

Otherwise, "make check-changes" will complain when we backport the change.

We need a recent test-network.sh to use new chutney features in CI.

Fixes bug 29703; bugfix on 0.2.9.1-alpha.

Since we have moved coveralls to the script target the entire build will
now fail if coveralls fail. We handle it more gracefully by echo'ing the
failure instead of doing a hard-failure.

See: https://bugs.torproject.org/29036

This should ensure that GCDA files are never entering the cache of
Travis CI.

See: https://bugs.torproject.org/29036

Already merged to 0.4.0 and later in tor-github/pr/776.
Backported to 0.2.9 and later with minor comment changes.

Part of 29706.

Allow connections to single onion services to remain idle without being
disconnected.

Relays acting as rendezvous points for single onion services were
mistakenly closing idle established rendezvous circuits after 60 seconds,
thinking that they are unused directory-fetching circuits that had served
their purpose.

Fixes bug 29665; bugfix on 0.2.1.26.