Add `-smbios type=2` to the libvirt config. Otherwise, the system is super buggy without it.

EDK II OVMF UEFI supports more resolutions than SeaBIOS. By setting resolution
in UEFI setup and Clover settings, it allows to use a larger resolution for a
more pixel perfect experience. The note includes some QEMU and VNC limitations
on resolution settings.

+ Fedora 27 is known to work.

+ Workaround for clock issues.

Due to popular demand, here is a working XML configuration file example for
macOS High Sierra. Includes some few instructions in the comment. Feel free to
amend it in your own push and close this PR.

I've tested it in Fedora 27 with stock qemu-kvm 2.10.1, so I've changed machine
to pc-q35-2.10 for a bit newer one and still works nicely so far. It's tested
with your provided OVMF_CODE-pure-efi.fd AND OVMF_VARS-pure-efi-1024x768.fd
only.

The main motivation of having libvirt XML file is the pretty straightforward
USB redirection to the guest, allowing to use it without dealing with system
session, root, changing permissions, selinux and such. SPICE protocol for
screen hypervisor also feels a bit faster refresh, mostly noticeable while
shaking windows with mouse pointer. VNC also works as expected if preferred.

The settings provided are not quite polished, maybe some libvirt and KVM modern
defaults make some features redundant, however.