[MINOR] uninline rb_insert_task_queue()

rb_insert_task_queue() was inlined and is quite large. Uninlining
it reduces code size by about 2 kB and slightly improves performance.
diff --git a/src/task.c b/src/task.c
index beddb27..b49bc74 100644
--- a/src/task.c
+++ b/src/task.c
@@ -47,7 +47,7 @@
 	rb_link_node(&newtask->rb_node, parent, p);
 }
 
-static inline void rb_insert_task_queue(struct task *newtask)
+static void rb_insert_task_queue(struct task *newtask)
 {
 	__rb_insert_task_queue(newtask);
 	rb_insert_color(&newtask->rb_node, newtask->wq);