fix for setBlob with large blob

I am using setBlob(int, Blob) with a 3.2GB large blob, but got the following stack trace.

java.lang.IndexOutOfBoundsException
	at java.io.BufferedInputStream.read(BufferedInputStream.java:327)
	at org.postgresql.jdbc2.AbstractJdbc2Statement.setBlob(AbstractJdbc2Statement.java:3073)

This patch fixes this problem for me.