Fixes CVE-2017-14859, CVE-2017-14860, CVE-2017-14862 and CVE-2017-14864. * gnu/packages/patches/exiv2-CVE-2017-14859-14862-14864.patch, gnu/packages/patches/exiv2-CVE-2017-14860.patch: New files. * gnu/local.mk (dist_patch_DATA): Register them. * gnu/packages/image.scm (exiv2)[source]: Use them.