allow hypervisor CPUID bit to be overriden

KVM defaults to the hypervisor CPUID bit to be set, whereas pure
QEMU clears it. On some occasions one wants to set or clear it the
other way round (for instance to get HyperV running inside a guest).

Move the bit-set to be done before the command line parsing and
enable it by default. One can disable it by using: -cpu qemu64,-hypervisor
Fix some whitespace damage on the way.

Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
