gnu: icecat: Label patches that have since been assigned CVEs.

Label patches that address the following CVEs: CVE-2017-5429, CVE-2017-5432,
CVE-2017-5433, CVE-2017-5434, CVE-2017-5435, CVE-2017-5436, CVE-2017-5438,
CVE-2017-5439, CVE-2017-5440, CVE-2017-5441, CVE-2017-5442, CVE-2017-5443,
CVE-2017-5444, CVE-2017-5445, CVE-2017-5446, CVE-2017-5447, CVE-2017-5448,
CVE-2017-5459, CVE-2017-5460, CVE-2017-5464, CVE-2017-5465, and CVE-2017-5469.

* gnu/packages/gnuzilla.scm (icecat)[source][patches]: Add comments indicating
CVE assignments.