CLEANUP: thread: rename __decl_hathreads() to __decl_thread()

I can never figure whether it takes an "s" or not, and in the end it's
better if it matches the file's naming, so let's call it "__decl_thread".
diff --git a/include/types/spoe.h b/include/types/spoe.h
index 562e9f2..aa3d5d1 100644
--- a/include/types/spoe.h
+++ b/include/types/spoe.h
@@ -275,7 +275,7 @@
 		struct list     applets;        /* all SPOE applets for this agent */
 		struct list     sending_queue;  /* Queue of streams waiting to send data */
 		struct list     waiting_queue;  /* Queue of streams waiting for a ack, in async mode */
-		__decl_hathreads(HA_SPINLOCK_T lock);
+		__decl_thread(HA_SPINLOCK_T lock);
 	} *rt;
 
 	struct {