Add a method for blocking threads on ports.

Additionally add the first lock class since we are becoming more
concurrent.

zion/lib/mutex.cpp

@@ -0,0 +1,11 @@
+#include "lib/mutex.h"
+
+#include "debug/debug.h"
+#include "scheduler/scheduler.h"
+
+void Mutex::Lock() {
+  while (__atomic_fetch_or(&lock_, 0x1, __ATOMIC_SEQ_CST) == 0x1) {
+    dbgln("Lock sleep: %s", name_);
+    gScheduler->Preempt();
+  }
+}