[vala] (19 commits) Non-fast-forward update to branch wip/singleton

[Rico Tzschichholz <ricotz src gnome org>]

The branch 'wip/singleton' 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:

  558e93a... Add support for singleton object classes

Commits added to the branch:

  e97489f... libvaladoc: Change link to Valadoc wiki page for HTML docle (*)
  12a560a... vala: Break reference chain between DataType and Symbol if  (*)
  cbb9215... vala: Allow read-only properties (*)
  e2f9b50... gtk+-4.0: Update to 3.94.0+14620423 (*)
  de80676... gstreamer: Update from 1.15+ git master (*)
  516d5bd... vapi: Update GIR-based bindings (*)
  7a2d5b9... gio-unix-2.0: Add DesktopAppInfo.launch_uris_as_manager_wit (*)
  ba32df8... glib-2.0: Add Process.spawn_async_with_fds() (*)
  391ec12... valadoc: Use HTML5 doctype in HTML doclet (*)
  204c7ba... codewriter: Output bodies of code-blocks if in VAPIGEN mode (*)
  03d4222... codegen: Let methods return -1 on error by default if possi (*)
  c185613... gidl: Properly resolve "time_t" (*)
  462f1cd... Regenerate GIDL-based bindings (*)
  cecaf40... gobject-2.0: Add lower_case_csuffix attributes to Type* sym (*)
  f59bb99... codegen: Allow TypeModule subclasses as parameter-type in m (*)
  d3f6389... girwriter: Add boolean GIR visible attribute to allow skipp (*)
  229199c... codegen: Fix invocation of abstract/virtual methods with No (*)
  84de995... vala: Report error for invalid base access in method/proper (*)
  1c1c96e... Add support for singleton object classes

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