the feature extractor.  Also added the necessary input validation
to make sure this feature doesn't get misused.

added some tests to make sure the code really does work with the
relaxed interface.

a copy by value.

for the assignment_function and sequence_labeler consistent.

computed.

missing asserts.

when the user uses the sequence label rejection feature.

svm_c_linear_trainer and svm_c_ekm_trainer objects.  However,
there was a bug which made them only ever do at most 16 iterations,
which is too few to solve many problems.  This has been fixed.