maint: Use consistent copyright.

maint: Use consistent copyright.

This is a follow up patch of commit f9ce7dad6, it modifies all
the files which declare the copyright like "See COPYING.LIB for
the License of this software" to use the detailed/consistent one.

And deserts the outdated comments like:

 * libvirt-qemu.h:
 * Summary: qemu specific interfaces
 * Description: Provides the interfaces of the libvirt library to handle
 *              qemu specific methods
 *
 * Copy:  Copyright (C) 2010, 2012 Red Hat, Inc.

Uses the more compact style like:

 * libvirt-qemu.h: Interfaces specific for QEMU/KVM driver
 *
 * Copyright (C) 2010, 2012 Red Hat, Inc.