Rename xentools30-hvm to xentools3-hvm to acknowledge that Xen dropped one

Rename xentools30-hvm to xentools3-hvm to acknowledge that Xen dropped one
digit in version numbers, and upgrade to 3.1.0.
Changes since 3.0.4:
    *   XenAPI 1.0 support
          o XML configuration files for virtual machines;
          o VM life-cycle management operations; and
          o Secure on- or off-box XML-RPC with bindings for many languages
    * Basic save/restore/migrate support for HVM (e.g. Windows) VMs;
    * Dynamic memory control for HVM guests;
    * 32-on-64 PV guest support (run PAE PV VMs on a 64-bit Xen!); and
    * Blktap copy-on-write disk support.

It also fixes some HVM bugs.
Note that this package contains a backport of the pcnet emulation from
xen-unstable, to make it useable. It gives better performances than the
default realtek emulation.