Move declarations in dump_entry_data_list to where the variables are used
Check memory allocations in dump_data_entry_list

This is a bit gross, as it only allows for one error code, but at least it
gets the public API right.
Update header file for earlier MMDB_free_entry_data_list var name change
Allow dump_entry_data_list to set a *status var to indicate errors

This allows us to return more than one type of error
Add MMDB_INVALID_DATA to MMDB_strerror and add handling for unknown error codes