Outliner: Set active modifier on click

The outliner already expands the panel for the modifier you click on,
this just extends that idea to also set it active, which is consistent
with behavior of active and selected items elsewhere in Blender.

source/blender/editors/space_outliner/outliner_select.c

@@ -1185,6 +1185,7 @@ static void outliner_set_properties_tab(bContext *C, TreeElement *te, TreeStoreE
           }
           else {
             ModifierData *md = (ModifierData *)te->directdata;
+            BKE_object_modifier_set_active(ob, md);
 
             switch ((ModifierType)md->type) {
               case eModifierType_ParticleSystem: