os: Expose power as is_running()

Author: fwsGonzo

api/kernel/os.hpp

@@ -84,6 +84,13 @@ class OS {
    */
   static void halt();
 
+  /**
+   *  Returns true when the OS will still be running, and not shutting down.
+   */
+  static bool is_running() {
+    return power_;
+  }
+
   /**
    *  Add handler for standard output.
    */