Suppress warnings of unused variables.

I will use them eventually when I implement all these functions.

I'm probably going to start CI work here soon, so I don't want warnings showing up in the logs unless they're important.

src/Filter.c

@@ -28,5 +28,7 @@
 HashMap *
 FilterApply(Filter * filter, HashMap * event)
 {
+    (void) filter;
+    (void) event;
     return NULL;
 }

src/Room.c

@@ -42,6 +42,8 @@ struct Room
 Room *
 RoomCreate(Db * db, RoomCreateRequest * req)
 {
+    (void) db;
+    (void) req;
     return NULL;
 }
 

src/Routes/RouteRoomAliases.c

@@ -37,6 +37,10 @@ ROUTE_IMPL(RouteRoomAliases, path, argp)
     Db *db = args->matrixArgs->db;
     DbRef *ref = NULL;
 
+    (void) roomId;
+
+    /* TODO: Placeholder; remove. */
+    goto finish;
 finish:
     DbUnlock(db, ref);
     JsonFree(request);

src/State.c

@@ -33,12 +33,14 @@
 static HashMap *
 StateResolveV1(Array * states)
 {
+    (void) states;
     return NULL;
 }
 
 static HashMap *
 StateResolveV2(Array * states)
 {
+    (void) states;
     return NULL;
 }