Merge branch 'master' into blender2.8

- Undo that changes modes currently asserts,
  since undo is now screen data.

  Most likely we will change how object mode and workspaces work
  since it's not practical/maintainable at the moment.

- Removed view_layer from particle settings
  (wasn't needed and complicated undo).

doc/doxygen/doxygen.intern.h

@@ -10,6 +10,10 @@
  *  \ingroup intern
  */
 
+/** \defgroup clog C-Logging (CLOG)
+ *  \ingroup intern
+ */
+
 /** \defgroup ctr container
  *  \ingroup intern
  */