[glib] (6 commits) ...Merge branch 'wip/chergert/marshall-matters' into 'master'

[Philip Withnall <pwithnall src gnome org>]

Summary of changes:

  266a292... gsignal: update documentation about va_marshaller (*)
  d7c1d47... gdbusobjectmanager: store signal ids for re-use (*)
  2a4b5ca... gobject: remove use of generic marshaller from GObject (*)
  273c00f... gio: ensure default va_marshaller is used (*)
  22ba441... gio: remove use of generic marshaller from GIO objects (*)
  b9e27b7... Merge branch 'wip/chergert/marshall-matters' into 'master'

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