This allows cross-type hash joins of these types together. Note that cross-type hash join can't be used yet as we need to set up an operator family. However an eventual hash index created now wouldn't be broken if we want to add this feature later.
PG 8.3 is missing other functions. Because current Ubuntu installs 8.4, supporting this version is already a good step.
This drops the need to handle the version number in any file and simplifies the test suite setup.
Note that for some reason the SumTable benchmark has gone more than twice faster than the previous run. Don't know what is the difference: probably the first run was with PostgreSQL from package manager and tne second with the one compiled myself. Will try to investigate more.