Use qemu-system- instead of kvm -m

As kvm -m doesn't work in Ubuntu 13.04 anymore.

libexec/start-target

@@ -14,8 +14,15 @@ fi
 
 case $VMSW in
   KVM)
-    [ -n "$KVM" ] || KVM=kvm
-    $KVM -cpu $ARCH -m ${VMEM:-2000} -smp ${NPROCS:-2} -drive file=target-$SUFFIX.qcow2,cache=writeback -net nic,model=virtio -net user,hostfwd=tcp:127.0.0.1:$VM_SSH_PORT-:22 -vnc 127.0.0.1:16 > var/target.log 2>&1 &
+    case $ARCH in
+        qemu32)
+            [ -n "$KVM" ] || KVM=qemu-system-i386
+            ;;
+        qemu64)
+            [ -n "$KVM" ] || KVM=qemu-system-x86_64
+            ;;
+    esac
+    $KVM -m ${VMEM:-2000} -smp ${NPROCS:-2} -drive file=target-$SUFFIX.qcow2,cache=writeback -net nic,model=virtio -net user,hostfwd=tcp:127.0.0.1:$VM_SSH_PORT-:22 -vnc 127.0.0.1:16 > var/target.log 2>&1 &
     echo $! > var/target.pid
     wait
     rm var/target.pid