[vala] (14 commits) Non-fast-forward update to branch wip/issue/767

[Rico Tzschichholz <ricotz src gnome org>]

The branch 'wip/issue/767' 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:

  1fa4a17... tests: Add "struct (un)boxing" variant test
  69d448d... WIP codegen: Implement silent-cast for GLib.Variant

Commits added to the branch:

  409136a... gio-2.0: Revert enum-typed flags parameters in Socket API (*)
  0c9534a... gstreamer: Update from 1.15.2+ git master (*)
  2d9c89e... vapi: Update GIR-based bindings (*)
  7d771a0... codegen: Move implicit GValue cast for comparison to Binary (*)
  6d71850... codegen: Use available *_unref functions in G_DEFINE_AUTOPT (*)
  126dee3... codegen: Handle "modulo" operation on floating-types in CCo (*)
  1f885e9... vala: Don't replace assignments for local variables with no (*)
  250f5a9... tests: Add "struct (un)boxing" variant test (*)
  a67b8ec... docs: Bump glib requirement in README.md (*)
  75a87e2... vala: Report error for unsupported operator instead of asse (*)
  73ce2cb... girparser: Create correct output in get_default_lower_case_ (*)
  d7dd578... gobject-introspection-1.0: Fix TypeInfo and TypeTag method  (*)
  e67b115... gstreamer-1.0: Fix TypeFind and TypeFindFactory method refe (*)
  54cfbdb... WIP codegen: Implement silent-cast for GLib.Variant

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