examples/c/ex_data_source.c:174:6: error: variable ‘is_snapshot_isolation’ set but not used [-Werror=unused-but-set-variable]
examples/c/ex_data_source.c:168:6: error: variable ‘ret’ set but not used [-Werror=unused-but-set-variable]
Move data source truncate method into WT_DATA_SOURCE.