Add sysinfo/smbios support to the QEmu driver

Add sysinfo/smbios support to the QEmu driver

The patch is based on the possiblity in the QEmu command line to
add -smbios options allowing to override the default values picked
by QEmu. We need to detect this first from QEmu help output.
If the domain is defined with smbios to be inherited from host
then we pass the values coming from the Host own SMBIOS, but
if the domain is defined with smbios to come from sysinfo, we
use the ones coming from the domain definition.

* src/qemu/qemu_conf.h: add the QEMUD_CMD_FLAG_SMBIOS_TYPE enum
  value
* src/qemu/qemu_conf.c: scan the help output for the smbios support,
  and if available add support based on the domain definitions,
  and host data
* tests/qemuhelptest.c: add the new enum in the outputs