cpu_map: Rewrite feature sync script

cpu_map: Rewrite feature sync script

Previously, the script would only detect differences between
libvirt's and qemu's list of x86 features, adding those features
to libvirt was a manual and error prone procedure.

Replace with a script that can generate libvirt's feature list
directly from qemu source code.

Usage: sync_qemu_features_i386.py [--output OUTPUT] [qemu]

If not specified otherwise, "output" defaults to x86_features.xml
in the same directory as sync_qemu_features_i386.py. If a checkout
of the qemu source code resides next to the libvirt directory, it
will be found automatically and need not be specified.

Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>