void append(int c) {
            token.append("\"");
            if (c == '\n') {
                token.append("\\n");
            } else if (c == '\r') {
                token.append("\\r");
            } else if (c == '"') {
                token.append("\\\"");
            } else if (c == '\\') {
                token.append("\\\\");
            } else {
                token.append("\\u").append(String.format("%04x", c & 0xffff));
            }
            token.append("\"");
        }
Removes leading and trailing quotation mark from the given string. This method will properly unescape whatever
content is withing the string literal as well.

@param str The string to unquote.
@return The unquoted string.
vespajlib/src/main/java/com/yahoo/javacc/UnicodeUtilities.java