Attempt to fix setMaxFieldSize() logic that was checked in yesterday.

I think this should fix the problem, but since I don't have a reproducable test
case, I can't be sure.  This problem is reported by Kim Ho of redhat, who will
test this fix.  This also includes a test case for the original functionality.

 Modified Files:
 	jdbc/org/postgresql/jdbc1/AbstractJdbc1Statement.java
 	jdbc/org/postgresql/test/jdbc2/ResultSetTest.java