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/log.h b/include/types/log.h
index ae7ce0b..cfafb91 100644
--- a/include/types/log.h
+++ b/include/types/log.h
@@ -220,7 +220,7 @@
 	int minlvl;
 	int maxlen;
 	struct logsrv *ref;
-	__decl_hathreads(HA_SPINLOCK_T lock);
+	__decl_thread(HA_SPINLOCK_T lock);
 };
 
 #endif /* _TYPES_LOG_H */