* gnu/build/vm.scm (load-in-linux-vm): Move Qemu network configuration from
ARCH-SPECIFIC-FLAGS to the Qemu command line. Use the "-nic" option of Qemu
instead of "-device" and "-net".
* gnu/system/vm.scm (common-qemu-options): Do not add a '-net' command.
(virtual-machine-compiler): Use "-nic user,..." instead of "-net".
* doc/guix.texi (Installing Guix in a VM, Invoking guix system, Running Guix
in a VM): Do the same for examples.