Bugfix/code clean using gcc warnings (#371)

* Enable extra GCC warnings to discover subtle bugs

* convert c++ comments to c comments

* cleanup pedantic compiler warnings

* Compile apps with GNU89 GNU99 GNU11 and GNU17

Co-authored-by: Steve Karg <skarg@users.sourceforge.net>

src/bacnet/basic/object/command.c

@@ -820,4 +820,5 @@ bool Command_Write_Property(BACNET_WRITE_PROPERTY_DATA *wp_data)
 
 void Command_Intrinsic_Reporting(uint32_t object_instance)
 {
+    (void)object_instance;
 }