commit 22da1d60a961cc178b4868e768af1389e2dfd43b
Author: fwarmerdam <fwarmerdam>
Date:   Fri Aug 24 20:47:49 2007 +0000

    _TIFFMergeFields() now only merges in field definitions that are missing.
    Existing definitions are silently ignored.  This avoids warnings with
    multi-directory files.
