Opencv sgjava

[sgjava]

Made generated delete() public instead of protected, so calling code can access.

Removed finalize() from Mat and added n_delete to release() to prevent native memory leaks.

[vpisarev]

👍

[sgjava]

✌️

[apavlenko]

Actually before these changes there were two options for Java API users: calling Mat::release() manually for immediate native memory freeing or leaving objects as is so they are released via Mat::finalize() call from the garbage collector. During tutorials on OpenCV Java API we suggested calling Mat::release() in Java code for more efficient memory management but still made possible to ignore this and let the garbage collector do its work.
I strongly suggest reverting the changes made by this PR before 3.0 release!!!

[apavlenko]

Also I'd like to note about the difference between Mat::release() and Mat object deletion: calling the 1st one we just free Mat memory allocated for the data, but the object is still usable again, while object deletion discards it totally. Please don't mix release() with delete!

[sgjava]

OK, I can separate the two again, but I'll add a releaseAndDelete(), so I don't have to do both in situations (most) that only release() is called.