xulrunner sdk is updated to version 23.0

Most recent version is 24.0 but Firefox on Ubuntu is 23 yet.
The (sdk)[(https://ftp.mozilla.org/pub/mozilla.org/xulrunner/releases/23.0/sdk/xulrunner-23.0.en-US.linux-i686.sdk.tar.bz2)] is from [Mozilla FTP site](https://ftp.mozilla.org/pub/mozilla.org/xulrunner/releases].