Create a builder for a Datum int-map.
Declared in <bdld_datumintmapbuilder.h>
DatumIntMapBuilder();
Optionally specify an initialCapacity for the int-map. If initialCapacity is not supplied, the initial capacity of the int-map is 0. Optionally specify an allocator (e.g., the address of a bslma::Allocator object) to supply memory; otherwise, the default allocator is used.