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>

apps/server/main.c

@@ -191,6 +191,7 @@ int main(int argc, char *argv[])
     uint32_t elapsed_seconds = 0;
     uint32_t elapsed_milliseconds = 0;
     uint32_t address_binding_tmr = 0;
+    BACNET_CHARACTER_STRING DeviceName;
 #if defined(INTRINSIC_REPORTING)
     uint32_t recipient_scan_tmr = 0;
 #endif
@@ -266,7 +267,6 @@ int main(int argc, char *argv[])
     }
     ucix_cleanup(ctx);
 #endif /* defined(BAC_UCI) */
-    BACNET_CHARACTER_STRING DeviceName;
     if (Device_Object_Name(Device_Object_Instance_Number(), &DeviceName)) {
         printf("BACnet Device Name: %s\n", DeviceName.value);
     }