Fix for 2 test cases of JDBC test suite

Attached is a patch that fixes 2 test cases of the JDBC test
suite. This reduces the number of failures from 9 to 7.

Both ConnectionTest and JBuilderTest did not create their own
tables, which caused these test cases to fail with "relation ...
does not exist". It appears these test cases relied on tables
created by the example code elsewhere in the source tree. I've
added the necessary "create table" and "drop table" statements
to the test cases, using the column definitions from the example
code.

While working on that I modified the helper method createTable
in JDBC2Tests.java to take a table parameter, rather than using
table names passed via the properties in build.xml. I'm not sure
what that was good for, and in fact, except for the default
table name "jdbctest", this functionality wasn't used at all.

Regards,
René Pijlman <rene(at)lab(dot)applinet(dot)nl>