Shrink the size of the VALUE_PAIR structure

Shrink the size of the VALUE_PAIR structure

Now that we're not writing strings to integer attributes,
we can dynamically change the size of the VALUE_PAIR.
It should be large enough to contain it's necessary fields,
and *only* enough of the VALUE_PAIR_DATA structure to contain
the type-specific data.  This means we save 250 bytes
of memory for every integer / date / ipaddr VALUE_PAIR.