patch - support for multi-dimensional arrays and NULL values

Hello Kris and hello group,
in the attachment you can find AbstractJdbc2Array class with two fixed
features: null value as element of an array and... multi-dimensional
arrays support. There are two things related with this two changes:
- all arrays are objects arrays (which means that e.g. boolean[] is
represented as Boolean[])
- when multi-dimensional array is processed then Object[] is returned by
getArray() - it's because we can't declare in Java an array of unknown
dimension (so if PostgreSQL returns char[][] then jdbc will return
Object[], that contains String[] elements)

Sorry that I didn't send patch file, but I didn't have time to install
cvs client (I'm using svn in everyday work).

In case of questions or any other discussion write me an email.

Best regards,
Marek Lewczuk