clang-format: use TypenameMacros

This commit removes line breaks and extra empty lines introduced in
commit fff3f79da9.

i3bar/include/outputs.h

@@ -73,6 +73,5 @@ struct i3_output {
     struct ws_head* workspaces;  /* The workspaces on this output */
     struct tc_head* trayclients; /* The tray clients on this output */
 
-    SLIST_ENTRY(i3_output)
-    slist; /* Pointer for the SLIST-Macro */
+    SLIST_ENTRY(i3_output) slist; /* Pointer for the SLIST-Macro */
 };