atom_* renamed to atomic_*; add mutex.*

mutex.h

@@ -0,0 +1,14 @@
+/*
+ * Copyright 2022 Oleg Borodin  <borodin@unix7.org>
+ */
+
+
+#include <stdint.h>
+
+typedef struct {
+    int32_t value;
+} mutex_t;
+
+void mutex_init(mutex_t* mutex);
+int32_t mutex_wait(mutex_t* mutex);
+int32_t mutex_post(mutex_t* mutex);