Add conventional #include guards to two header files

src/commands/LoadCommands.h

@@ -9,6 +9,9 @@
 
 **********************************************************************/
 
+#ifndef __AUDACITY_LOAD_COMMANDS__
+#define __AUDACITY_LOAD_COMMANDS__
+
 #include "audacity/ModuleInterface.h"
 
 #include <functional>
@@ -85,3 +88,5 @@ private:
    using CommandHash = std::unordered_map< wxString, const Entry* > ;
    CommandHash mCommands;
 };
+
+#endif