Add thread.Pool with example in demo.odin; Update linalg to support handness changes for projection matrices

core/thread/thread_unix.odin

@@ -155,3 +155,8 @@ destroy :: proc(t: ^Thread) {
 	t.unix_thread = {};
 	free(t);
 }
+
+
+yield :: proc() {
+	unix.pthread_yield()
+}