qemu: Add QEMU 2.10 x86_64 the generated capabilities
For reference, these were generated by updating a local qemu git
repository to the latest upstream, making sure the latest dependencies
were met via "dnf builddep qemu" from my sufficiently privileged root
account, checking out the v2.10.0 tag, and building in order to generate
an "x86_64-softmmu/qemu-system-x86_64" image.
Then using a clean libvirt tree updated to master and built, the image
was then provided as input: