COPY support implemented

With the introduction of the V3 protocol in 7.4 it is now possible to
support the COPY protocol in the JDBC driver. Before it was impossible to
recover from errors and the Connection had to be abandoned. This patch
implements support for COPY based on the API proposed by Michael
Adler's original patch of about a year ago.

For example

Connection conn = DriverManager.getConnection(...);
CopyManager copy = ((org.postgresql.PGConnection)conn).getCopyAPI();

// copy data from the table to the given output stream
OutputStream output = new ByteArrayOutputStream();
copy.copyOut("tablename",output);

// copy data from the given input stream to the table
InputStream input = new ByteArrayInputStream(output.toByteArray());
copy.copyIn("tablename",input);

Kris Jurka