ClangFormat: apply to source, most of intern

Apply clang format as proposed in T53211.

For details on usage and instructions for migrating branches
without conflicts, see:

https://wiki.blender.org/wiki/Tools/ClangFormat

source/blender/compositor/nodes/COM_MixNode.h

@@ -26,8 +26,8 @@
  * \ingroup Node
  */
 class MixNode : public Node {
-public:
-	MixNode(bNode *editorNode);
-	void convertToOperations(NodeConverter &converter, const CompositorContext &context) const;
+ public:
+  MixNode(bNode *editorNode);
+  void convertToOperations(NodeConverter &converter, const CompositorContext &context) const;
 };
 #endif