[gtk+] (9 commits) Non-fast-forward update to branch wip/baedert/symbolic-icons

[Timm Bäder <baedert src gnome org>]

The branch 'wip/baedert/symbolic-icons' 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:

  3a44d3f... csstypes: Add GTK_CSS_AFFECTS_SYMBOLIC_ICON
  7efd2cd... stylepropertyimpl: Use GTK_CSS_AFFECTS_SYMBOLIC_ICON
  9f4fca8... iconhelper: Safe whether the surface is symbolic
  e297d26... iconhelper: Un-duplicate some code
  6781a94... GtkImage: Do not always invalidate the icon helper
  4f111b2... iconhelper: Don't invalidate unnecessarily
  b01c3e5... Remove more unnecessary redraws
  615b1e1... cssstylechange: Add helper function to print change

Commits added to the branch:

  f60e144... Document rem as CSS unit (*)
  58303c2... csstypes: Add GTK_CSS_AFFECTS_SYMBOLIC_ICON
  7e23bee... stylepropertyimpl: Use GTK_CSS_AFFECTS_SYMBOLIC_ICON
  f5aef4e... iconhelper: Safe whether the surface is symbolic
  76c72ea... iconhelper: Un-duplicate some code
  96f7b02... GtkImage: Don't always invalidate the icon helper
  1eab646... iconhelper: Don't invalidate unnecessarily
  88f3e65... Remove more unnecessary redraws
  ff35494... cssstylechange: Add helper function to print change

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