Removed superfluous cast.

tests/threads.c

@@ -53,7 +53,7 @@ static void error_callback(int error, const char* description)
 
 static int thread_main(void* data)
 {
-    const Thread* thread = (const Thread*) data;
+    const Thread* thread = data;
 
     glfwMakeContextCurrent(thread->window);
     glfwSwapInterval(1);