Cleanup: spelling in comments & minor cleanup

Also hyphenate 'mouse-move' use doxy sections in render_update.c &
move function comment from the header to the source.

source/blender/editors/physics/particle_edit.c

@@ -4667,7 +4667,7 @@ typedef struct BrushEdit {
   int lastmouse[2];
   float zfac;
 
-  /* optional cached view settings to avoid setting on every mousemove */
+  /** Optional cached view settings to avoid setting on every mouse-move. */
   PEData data;
 } BrushEdit;