- also some minor changes to the respective sample cpp file

* expose 2 extra methods from ml::TrainData: getNames() and getVarSymbolFlags(). The first one returns text labels from CSV (if the data has been loaded from CSV); the second one returns a matrix of boolean values; its n-th element is 1 iff the corresponding column in the CSV uses symbolic names, not numbers.

* check that the dynamic_cast succeeds

* Add Grana's connected components algorithm for 8-way connectivity. That algorithm is faster than Wu's one (currently implemented in opencv). For more details see https://github.com/prittt/YACCLAB.

* New functions signature and distance transform compatibility

* Add tests to imgproc/test/test_connectedcomponents.cpp

* Change of test_connectedcomponents.cpp for c++98 support

strong and retain are synonymous but using strong along with  obsolete synonym retain in one file is negligent

Enable SSE optimization

  * DRY
  * switch to Cv32suf and remove fp32Int32
  * add Cv16suf

- one test for type_id;
- another for comments in JSON;

Fixes spelling in comment

resolve undeclared identifier close error

The Mat "src_copy" is never used.