Manipulator: changes for overlay options

There are now 3 categories in the overlay popover:

- Navigation
- Active (camera, lamp... etc)
- Tool (manipulator)

The user preference for mini axis now controls if the mini axis
displays minimal or a full-interactive widget.

Part of design: T55863

source/blender/editors/transform/transform.h

@@ -505,7 +505,7 @@ typedef struct TransInfo {
 
 	short		current_orientation;
 	TransformOrientation *custom_orientation; /* this gets used when current_orientation is V3D_MANIP_CUSTOM */
-	short		twflag;			/* backup from view3d, to restore on end */
+	short		mpr_flag;			/* backup from view3d, to restore on end */
 
 	short		prop_mode;