changes

[ChadDavis]

I'm upgrading from a very old version of lucene to 2.4  I tried to research
all the possible changes, this included reading the change file from the 2.4
version, which appears to reach back through all of the versions.  However,
I'm finding major API changes that aren't documented in that file.  For
example, Field.Keyword() is gone.  Shouldn't I find this in that change log?