gnu: icecat: Rename patches to indicate CVE assignments.

This documents that we include fixes for the following CVEs: CVE-2017-5472,
CVE-2017-7749, CVE-2017-7750, CVE-2017-7751, CVE-2017-7752, CVE-2017-7754,
CVE-2017-7756, CVE-2017-7764, CVE-2017-7765, CVE-2017-7778, and that we
include 15 out of 20 patches for CVE-2017-5470.

* gnu/packages/gnuzilla.scm (icecat)[source]: Rename existing patches to
indicate their CVE assignments.