Growing by a factor lower than the golden ratio increases the chances of
reusing memory freed from earlier allocations. Set growth rate to 1.5
which also reduces internal fragmentation.
xmlGrowCapacity makes sure that dynamic arrays don't grow beyond an
explicit maximum size. size_t considerations are also taken into account.
A macro XML_MAX_ITEMS is provided as default maximum with value
1 billion.
When fuzzing, the initial size is set to 1 to cause more reallocations.
This can require adjustments if callers really need larger arrays.
