Due to the explicitly declared copy constructor Vec<T, n>::Vec(Vec <T,n>&)
GCC 9 warns if there is no assignment operator, as having one typically
requires the other (rule-of-three, constructor/desctructor/assginment).

As the values are just a plain array the default assignment operator does
the right thing. Tell the compiler explicitly to default it.
Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>

* dnn: fix BNLLLayer implementation

details: https://github.com/BVLC/caffe/blame/1.0/src/caffe/layers/bnll_layer.cpp#L17

* dnn: enable OCV/OpenCL BNLL layer

Keep a local copy of `features` from `flann::GenericIndex ` constructor (#14898)

* Fix warnings on Windows

* Fix #4376

Old flag resulted in software implementation being selected when the Intel decoder is not the primary adapter.

- ReadProtoFromTextFile
- ReadProtoFromTextBuffer

* tensorflow support mirror pad

* revert macro define

* revert macro define

* reduce code duplication

* revert macro define

requires CMake 3.14+

* Support Eltwise3d

* Refactoring

* Fix test