Regression: Problems with Timestamp arguments

  Hello colleagues,

  There seems to be a problem with the latest driver and Timestamp
arguments uses in IS NULL comparisons:
  QUERY:     SELECT ? IS NULL
  ARGUMENTS: statement.setTimestamp(1, new
Timestamp(System.currentTimeMillis()))

  Result:
Exception in thread "main" org.postgresql.util.PSQLException: ERROR:
could not determine data type of parameter $1
    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2157)
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1886)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:255)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:555)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:417)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:302)

  The problem arises on:
  protocolVersion=3, or not specifying protocol version
  argument type: Timestamp

  The problem does not arise on other types (tested on BigDecimal and String)
  The problem does not arise when using protocolVersion=2
  The problem does not arise if the expression is not ? IS NULL

  List of work-around methods:
  - Degrade the protocol:
   jdbc:postgresql://host:port/database?protocolVersion=2
   * does not work with PgPool-2

  - Explicitly cast the argument
   SELECT ?::timestamp IS NULL
   SELECT CAST(? AS timestamp) IS NULL
   * requires rewriting of currently working code

  I believe this to be a bug.