On 14th of October Tome Lane committed new patch from Itagaki Tahahiro:
Log Message: ----------- Support SQL-compliant triggers on columns, ie fire only if certain columns are named in the UPDATE's SET list. Note: the schema of pg_trigger has not actually changed; we've just started to use a column that was there all along. catversion bumped anyway so that this commit is included in the history of potentially interesting changes to system catalog contents. Itagaki Takahiro