DITA XML output generator should write 0x0 as 0.

The value attribute of the cxxEnumeratorInitialiser tag can be 0x0 or 0x00 etc, but some publishers treat this value as the null value. Enumerator values appear in hex when they are used for setting bits on and off. But when the actual value is 0, there is no need to write the value in hex, so change the output generator to write 0 instead of 0x0.