libostree v2017.3

[Colin Walters <walters verbum org>]

https://github.com/ostreedev/ostree/releases/tag/v2017.3

A variety of small fixes here.  One of the most notable things is
the static delta progress computation is now more accurate; this should
make it easier to write a user interface consuming libostree that displays
how much will be downloaded before initiating it.

Related to this, `ostree admin upgrade` gained `--pull-only` and `--deploy-only`
which makes it easier to write e.g. a systemd timer unit that does background
pulls, but only do a deployment (i.e. upgrade) on administrator/device owner
action.  A bit more information in <https://github.com/ostreedev/ostree/pull/642>
and <https://github.com/ostreedev/ostree/issues/640>

There are two API additions - it's now possible to [configure the progress UI 
frequency](https://github.com/ostreedev/ostree/pull/725)
and [the zlib compression level](https://github.com/ostreedev/ostree/pull/721).

Besides that, there are a variety of smaller fixes.  My favorite is probably
a small fix for [grub2 on ppc64](https://github.com/ostreedev/ostree/pull/716),
so we now have `fedora/26/ppc64le/atomic-host`.

Thanks to all contributors!

```
Christian Hergert (1):
      repo/checkout: fix 32-bit builds

Colin Walters (28):
      deltas: Don't put unreadable *from* objects in fallback
      delta-show: Don't dump whole superblock, do show fallback checksums
      repo: Fix static delta progress display
      pull: Explicitly error out if metadata objects are fallbacks
      pull: Fold together deltapart+fallback count for display
      ci: Install PyYAML
      lib: Ensure an error is set in ensure_unlinked() if errno != ENOENT
      libtest: Re-enable quiet mode for building fs tree
      README.md: Add more/clean up links to consuming projects
      libglnx: Re-bump to master due to accidental reversion
      ci: Hard error on all -fsanitize=undefined warnings
      build: Add --with-smack, use it to reset contexts for writing objects
      main: Make ostree --version output YAML (and add gitrev)
      deploy: Correctly use libmount unref() calls rather than free()
      man/repo-config: Document mirrorlist
      tree-wide: Squash noncritical compiler warnings
      deploy/libmount: Fix build with old util-linux 2.23 (CentOS7)
      fetcher: Log failures into journal
      upgrade: Add support for --pull-only and --deploy-only
      grub2: Use g_spawn_sync() rather than GSubprocess to avoid SIGCHLD
      grub2: Use "linux16" only on x86/x86_64
      pull: Use all available commits for delta sources
      fetcher/curl: Fix leaks caught by ASAN
      Allow and start using C99 declaration-after-statement
      repo/checkout: Verify early if src/destination are on same device
      checkout: Support a "pure addition" mode
      repo/checkout: Convert a few functions to new "stmt-decl/FALSE" style
      Release 2017.3

Gatis Paeglis (1):
      deltas: Expose the filename parameter

Georges Basile Stavracas Neto (2):
      repo-pull: add option to set the async update frequency
      ostree: allow setting update frequency from command line

Giuseppe Scrivano (1):
      contrib/golang: rm directory

Jonathan Lebon (2):
      pull: don't use static deltas if archive repo
      libglnx: bump for -Wmaybe-uninitialized fix

Philip Withnall (2):
      build: Fix disabling --enable-man if xsltproc is not available
      libostree: Allow compression level to be set for archive-z2 stream
```

Git-EVTag-v0-SHA512: 
55adebf589a0f2115f0ab3cb3f69b42ba3a08c19b3bf54580c437ac08e336651d54849666ab5718e466bdc99bbbaedca79f91619d6e5db3a0f15849029d33cfe