Resolves warning from Oracle Parfait static analyser:
Error: Unchecked result
Unchecked result [unchecked-result-call-X]:
Unchecked return value from call to XOpenDisplay. Value display must be ch
ecked to ensure this function was successful.
at line 73 of hw/dmx/examples/xbell.c in function 'main'.
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>