update C3P0 for more compatiblity.

[loopx9]

The PoolBackedDataSource class within this payload is not nesscessary, and it does not declare a static serialVersionUID, that may get different serialVersionUID from various versions of C3P0. But the PoolBackedDataSourceBase class has a hard-coded serialVersionUID, so removing PoolBackedDataSource can make this payload more compatible with other versions of C3P0.