Enable exclusive locking of stripe files on all platforms, not just Windows and
O_EXLOCK.

Use this support (moved out of NamedLock) to massively simplify NamedLock.

Add support for shared file locks, and ensure that opening files respects any
exclusive (advisory) lock on that file.

Stop lying about our refcount when creating new files in BackupFileSystem.

Should fix random test failures due to housekeeping process realising that the
master has asked it to terminate, and logging that it has, after the master has
already died and the test finished, confusing the test runner with its extra
output. Should also help make the occasionally-reported housekeeping crashes
more obvious and easier to debug.

(cherry picked from commit 0100d318)
(cherry picked from commit 2cc729b45d60f3c9b920a459538171882a564b0d)

Include a message in the exception, and reuse code to make them consistent.

Whitespace cleanup.

(cherry picked from commit 8589bd9a)

See https://github.com/boxbackup/boxbackup/issues/16 for details. Thanks to
Chris West @FauxFaux for the initial patch!

Use OpenSSL 1.1.0g for Windows superbuild.

Fix Windows build by removing calls to obsolete do_ms.bat
<https://stackoverflow.com/questions/39076244/why-there-is-no-ms-do-ms-bat-after-perl-configure-vc-win64a/39247560#39247560>.

Workaround for incorrect library suffixes searched by FindOpenSSL
<https://gitlab.kitware.com/cmake/cmake/issues/17604>.

Link OpenSSL statically and fix missing dependency on crypt32.lib.

(cherry picked from commit edd3687f067c68b131822e0064cdeff5bf7a3835)
(cherry picked from commit b003e009d1fccadf55a0f59a01c66f7b80f9b3e5)
(cherry picked from commit cc6e20466b857f7e20d816a2c20cb36f112398ab)
(cherry picked from commit 303c6405e3bc1e673dbc691792e0633742c01f4e)
(cherry picked from commit 4e24006f75142a254f1a7db76cf9da1e752d9283)
(cherry picked from commit 448ac48a89538f67f508f8d21931c5e6e90472c0)
...

Define our own preprocessor defines for lock methods, test that we cover every
case at compile time ad that they have the semantics that we expect (reentrant
or not).

Add support for F_OFD_SETLK, a non-reentrant lock type offered by Linux, and
ensure that this and FLOCK are chosen in preference to F_SETLK locks, which are
reentrant.

(cherry picked from commit de1911b1)
(cherry picked from commit 96136adf)

Should improve code readability and robustness.

(cherry picked from commit e773e4cc)

By separating their roles (which used to overlap) it's now possible to run a
forking server in the foreground, or a non-forking daemon in the background,
which can be useful for debugging (for example, to more closely simulate how
test daemons work on Windows when running on Unix). -DF is now needed to
have a non-forking server in the foreground.

(cherry picked from commit b31c0e4abd4875bb25ff7a918ed5bc7f7faf595d)

These exceptions are used to communicate state to the caller, and should not be
treated as errors in common cases.

(cherry picked from commit 86f3e9c0f4916741bbed20e04a4b4f2d71bb4f32)

Make testbackupstorepatch do housekeeping in-process to make debugging easier.
Check return value of housekeeping to ensure that no errors were detected.

We expect that the raidfile or HTTP file doesn't exist during CreateAccount, so
the exception message is unhelpful, so suppress it.

Replace with BackupFileSystem::GetLock where used (only in tests at this
point).

After calling its Install() method, the guard will be installed in the central
logging configuration, and will automatically be uninstalled when the object
goes out of scope and is destroyed.

(cherry picked from commit 2b5b65b2dccfa2a88688e0103dc4996a039c515c)

This should help diagnose occasional locking problems causing test failures on
AppVeyor.

(cherry picked from commit 94f75ac0476c2264ed80f51c5d4014639dccb407)

(cherry picked from commit c38e93f2)

This logging is categorised, so it can be enabled with fine-tuning using the -L
command-line option.

(cherry picked from commit 7a2572c446b4a95f18eda04e72f6aabfd9544e04)

Implement as a specialised test, and run on S3 as well.

This requires implementation of S3BackupFileSystem::DeleteFile and
DeleteDirectory, and a version of change_account_limits which takes a
reference to a BackupAccountControl.

Don't swallow exceptions by returning before rethrowing them