Permanently enabled the asserts in the object detector test functions

since it's easy to mix up the adjust threshold and epsilon arguments
and these checks will usually catch that.  The checks are also very
low cost.

dlib/svm/cross_validate_object_detection_trainer.h

@@ -96,7 +96,7 @@ namespace dlib
     )
     {
         // make sure requires clause is not broken
-        DLIB_ASSERT( is_learning_problem(images,truth_dets) == true &&
+        DLIB_CASSERT( is_learning_problem(images,truth_dets) == true &&
                      0 < overlap_eps && overlap_eps <= 1,
                     "\t matrix test_object_detection_function()"
                     << "\n\t invalid inputs were given to this function"
@@ -226,7 +226,7 @@ namespace dlib
     )
     {
         // make sure requires clause is not broken
-        DLIB_ASSERT( is_learning_problem(images,truth_dets) == true &&
+        DLIB_CASSERT( is_learning_problem(images,truth_dets) == true &&
                      0 < overlap_eps && overlap_eps <= 1 &&
                      1 < folds && folds <= static_cast<long>(images.size()),
                     "\t matrix cross_validate_object_detection_trainer()"