[5073a] Augmented syntax

src/bin/dhcp4/dhcp4_lexer.ll

@@ -471,6 +471,7 @@ ControlCharacterFill            [^"\\]|\\{JSONEscapeSequence}
 \"option-def\" {
     switch(driver.ctx_) {
     case isc::dhcp::Parser4Context::DHCP4:
+    case isc::dhcp::Parser4Context::CLIENT_CLASSES:
         return isc::dhcp::Dhcp4Parser::make_OPTION_DEF(driver.loc_);
     default:
         return isc::dhcp::Dhcp4Parser::make_STRING("option-def", driver.loc_);

src/bin/dhcp4/dhcp4_parser.yy

@@ -1535,6 +1535,7 @@ not_empty_client_class_params: client_class_param
 
 client_class_param: client_class_name
                   | client_class_test
+                  | option_def_list
                   | option_data_list
                   | next_server
                   | server_hostname