Transforms tcindex to use tcf_exts API and thus adds support for
actions. Replaces the existing change implementation with a new one
supporting changes for existing filters which allows to change a
classifier without letting a single packet pass by unclassified.

Fixes various cases where a error is returned but the filter was
changed already.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>