* gnu/packages/patches/x265-arm-flags.patch: Update patch.
* gnu/packages/video.scm (x265): Update to 3.4.
[arguments]: Remove obsolete substitution. Disable the newly-added assembly
optimizations on AArch64, as they are not implemented for all targets we build.
* gnu/packages/video.scm (x265)[patches]: Add patch.
[arguments]: Add a configure-flag to disable assembly. Adjust a custom
phase to recognize armv8 as 32-bit arm when masquerading as armhf-linux.