Handle Java 9 additions of covariant return types to java.nio.ByteBuffer methods

Java 9 introduces overridden methods with covariant return types for the following methods in java.nio.ByteBuffer that are used by the driver:

• position
• limit
• flip
• clear

In Java 9 they all now return ByteBuffer, whereas the methods they override return Buffer,
resulting in exceptions like this when executing on Java 8 and lower:

java.lang.NoSuchMethodError: java.nio.ByteBuffer.limit(I)Ljava/nio/ByteBuffer

This is because the generated byte code includes the static return type of the method, which is not found on Java 8 and lower because the overloaded methods with covariant return types don't exist.

The solution is to cast ByteBuffer instances to Buffer before calling the method.