gnu: icecat: Apply fixes for CVE-2015-{0817,0818} and other selected bugs.
* gnu/packages/patches/icecat-CVE-2015-0817.patch,
gnu/packages/patches/icecat-CVE-2015-0818-pt1.patch,
gnu/packages/patches/icecat-CVE-2015-0818-pt2.patch,
gnu/packages/patches/icecat-bug-1127780.patch,
gnu/packages/patches/icecat-bug-1144991.patch,
gnu/packages/patches/icecat-bug-1145870.patch,
gnu/packages/patches/icecat-bug-1146339.patch: New files.
* gnu-system.am (dist_patch_DATA): Add them.
* gnu/packages/gnuzilla.scm (icecat): Add patches.