Expose also the virDomainModificationImpact constants
Expose also the virDomainModificationImpact constants

These are required when invoking the virDomainSetMetadata API

Signed-off-by: Flavio Castelli <d1035a58d87d0b7918844ad2fd699273faf2f5d5@suse.com>

rgbkrk/libvirt-go,libvirt/libvirt-go,alexzorin/libvirt-go,libvirt/libvirt-go,alexzorin/libvirt-go,Pryz/libvirt-go,libvirt/libvirt-go,Pryz/libvirt-go,libvirt/libvirt-go,Pryz/libvirt-go,rgbkrk/libvirt-go,rgbkrk/libvirt-go