[vala] (2 commits) Non-fast-forward update to branch staging

[Rico Tzschichholz <ricotz src gnome org>]

The branch 'staging' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  91b0fd6... girparser: TypeSymbol of accessor must match the property
  9a9eb1e... girparser: Make property inherit nullable attribute from ge
  60454cd... vapi: Regenerate to pick up nullable attribute of property 

Commits added to the branch:

  0fa66ca... Sync NEWS from 0.52 (*)
  5bf9d83... codegen: Allow null to initialize non-null struct inside in

(*) This commit already existed in another branch; no separate mail sent