function raise(pos, message) {
    var loc = getLineInfo(input, pos);
    message += " (" + loc.line + ":" + loc.column + ")";
    var err = new SyntaxError(message);
    err.pos = pos;
    err.loc = loc;
    err.raisedAt = tokPos;
    throw err;
  }
This function is used to raise exceptions on parse errors. It
takes an offset integer (into the current `input`) to indicate
the location of the error, attaches the position to the end
of the error message, and then raises a `SyntaxError` with that
message.

@param {number} pos
@param {string} message
@throws {SyntaxError}