By reusing the qjson test suite.  After checking that we can demarshal, marshal
again and compared to the expected decoded value.  This doesn't work so well
for floats because they cannot be accurately represented in decimal but we
try our best.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>