A notable feature is that we now support a more complete
"selector" syntax in libdnf terminology - this means we
honor RPM `Provides` and version specifications both
in treecompose and for package layering.

For packagers, note that this drops a depenency on libgsystem.

Otherwise, there are some smaller bugfixes and CI cleanup.

```
Colin Walters (25):
      build-sys: Bump to -std=gnu11
      daemon: Fix use of a potentially uninitialized variable
      tree-wide: Remove some unused variables found by CLang
      tree-wide: Port away from gs_transfer_out_value()
      tree-wide: Drop the last libgsystem autocleanup usage
      compose: Port a large chunk of postprocessing to fd-relative
      libglnx: Update to master (for -fsanitize=undefined fixes)
      core: Fix lock directory initialization
      tree-wide: Remove more unused variables
      tree-wide: Fix use of incorrect flag type
      tree-wide: Fix use of potentially uninitialized variables
      Add .redhat-ci.yml
      compose: Honor --dry-run --touch-if-changed
      compose: Create rootdir more directly, use fd-relative
      postprocess: Drop use of gs_file_rename(), use fd-relative
      postprocess: Port tmpfiles.d-copying code to fd-relative
      postprocess: Drop a libgsystem use in add-files
      postprocess: More fd-relative-ification
      postprocess: Port remaining libgsystem call sites
      libpriv: Pull in copy of gs_file_get_path_cached()
      Final removal of libgsystem dependency
      libdnf: Update to latest master
      redhat-ci: Update to match ostree
      tests: Test pinned package version
      Release 2016.12

Jonathan Lebon (2):
      upgrader: small amendment to previous commit
      daemon: use refspec after pulling ancestry
```

Git-EVTag-v0-SHA512: feab5b34b840716022d6ed8713dbe4c403ed91d92273affb27dd6ec9682d475bf0c13ee3f69c7b34f729d83efe9da16e60badf5819886612e0d331e6af45357b