Added unit tests for the new sequence labeling stuff

dlib/test/CMakeLists.txt

@@ -87,6 +87,7 @@ set (tests
    reference_counter.cpp
    scan_image.cpp
    sequence.cpp
+   sequence_labeler.cpp
    serialize.cpp
    set.cpp
    sldf.cpp

dlib/test/makefile

@@ -102,6 +102,7 @@ SRC += read_write_mutex.cpp
 SRC += reference_counter.cpp
 SRC += scan_image.cpp
 SRC += sequence.cpp
+SRC += sequence_labeler.cpp
 SRC += serialize.cpp
 SRC += set.cpp
 SRC += sldf.cpp