attempt at a patch to 7.1.2 to support Array.

[I think I've solved the mangled patch problem.  Hotmail seems to
try to format the text file, so gzipping it should solve this
problem.]

In this patch I've incorporated Barry's feedback.  Specifically:

1)  OIDs are no longer hard-coded into Array.java.  In order to
    support this change I added a getOID(String) method to Field.java
    which receives a PostgreSQL field type and returns a value from
    java.sql.Types.  I couldn't get away from using OIDs altogether
    because the JDBC spec for Array specifies that some methods return
    a ResultSet.  This requires I construct Field objects,
    which means I need OIDs.  At least this approach doesn't hard
    code these values.  A Hashtable cache has been added to Field
    so that an SQL lookup isn't necessary (following the model already
    in Field.java).

2)  Rewired the base formatting code in ResultSet.java to use 'to'
    methods, which are then exposed as static methods in ResultSet.
    These methods are used in Array to format the data without
    duplications in the code.

3)  Artifact call to first() in ResultSet.getArray() removed.

Greg Zoller