Improve change descriptions to note FTFBSs

debian/changelog

@@ -4,6 +4,8 @@ ostree (2017.12-2) UNRELEASED; urgency=medium
     in particular for architecture-specific builds. Note that it remains
     in Build-Depends (not Build-Depends-Indep) because it is also needed
     for gtkdocize during dh_autoreconf.
+    - In particular this might fix FTBFS on sparc64, where highlight(1)
+      fails.
   * d/p/2017.13/lib-core-Init-struct-stat-buffer.patch,
     d/p/2017.13/lib-sysroot-Fix-pointer-going-out-of-scope-in-unlock-code.patch,
     d/p/2017.13/lib-deploy-Ignore-FIFREEZE-FITHAW-errors-when-already-in-.patch,
@@ -15,6 +17,8 @@ ostree (2017.12-2) UNRELEASED; urgency=medium
     d/p/2017.13/lib-repo-Properly-handle-NULL-homedir-when-signing-commit.patch,
     d/p/2017.13/lib-repo-Fix-loading-commitstate-with-parent-repos.patch:
     Add various bugfix patches from upstream
+    - In particular, dealing with the possibility that EOPNOTSUPP != ENOTSUP
+      should fix test failures on hppa.
   * d/p/2017.13/tests-Add-test-pull-bareuseronly.patch:
     Add more test coverage from upstream