jdbc: Support transaction savepoints #177

conn.createStatement();
int rows = stmt.executeUpdate("INSERT INTO TAB1 (COL1) VALUES (’FIRST’)");
Savepoint svpt1 = conn.setSavepoint("SAVEPOINT_1");
rows = stmt.executeUpdate("INSERT INTO TAB1 (COL1) VALUES (’SECOND’)");
conn.rollback(svpt1);
conn.commit();