Update changelog
This mentions the reduction in memory allocations in
MMDB_get_entry_data_list().
+* Perform fewer memory allocations in `MMDB_get_entry_data_list()`. This
+ significantly improves its performance. GitHub #147.
* Fix `mmdblookup`'s build epoch reporting on some systems. Big endian
systems with a 32-bit `time_t` no longer show a database build date of
1970-01-01 00:00:00. Pull request by Rainer Jung. GitHub #143.
