Switch to the C++17 fallthrough attribute.

src/command_parse.cpp

@@ -428,7 +428,7 @@ void CommandParser::TranslateSingleParam(TranslateType to, const std::string& it
 			}
 			// If no custom translator was given, fall through
 		}
-		/*@fallthrough@*/
+		[[fallthrough]];
 		default:
 			/* Do nothing */
 			dest.append(item);

src/configparser.cpp

@@ -362,7 +362,7 @@ struct Parser
 					case 0xFE:
 					case 0xFF:
 						stack.errstr << "Do not save your files as UTF-16 or UTF-32, use UTF-8!\n";
-						/*@fallthrough@*/
+						[[fallthrough]];
 					default:
 						throw CoreException("Syntax error - start of tag expected");
 				}