[gtk+] (23 commits) ...window: Avoid a set-but-not-used warning

[Timm Bäder <baedert src gnome org>]

Summary of changes:

  006f2e3... testheaderbar: Fix custom CSS (*)
  8312ee0... testsuite: Add selected gl renderer test node files (*)
  3158b48... testoutsetshadowdrawing: Add adwaita CSD window test case (*)
  a720a63... gl renderer: Insert render target op in render_texture path (*)
  a61eecc... snapshot: Don't create clip nodes with 0 width or height (*)
  9675b8a... showrendernode: Add some advanced options (*)
  9f26740... gl renderer: Properly flip texture in render_texture path (*)
  e1c1206... tests: Fix the unblurred gl renderer output images (*)
  767df91... testsuite: Move gl renderer nodes files into their own dire (*)
  c4d5225... testoutsetshadowdrawing: Add more samples (*)
  2bc10fa... gl renderer: draw all outset shadows (*)
  aeaab55... gl renderer: Only draw what we have to (*)
  4abbf92... gl renderer: Remove some unused uniforms from shader (*)
  825608a... gl renderer: Remove unused parameter (*)
  352590c... gl driver: Remove vao API (*)
  c9656e2... gl driver: Only support one fbo per texture (*)
  1cbd4d2... gl driver: Remove dead warning code (*)
  d2d18f7... gl driver: Remove gl-context property (*)
  e0436b3... gl renderer: Properly delete all shader programs (*)
  6587864... gl driver: Remove more unused API (*)
  86a6131... build: Rename a variable (*)
  f92cca5... gl renderer: Fix release build
  c1573a1... window: Avoid a set-but-not-used warning

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