see https://github.com/Itseez/opencv/pull/3137

Conflicts:
	modules/core/src/matmul.cpp

A self-assignment leads to a call of release() with refcount being 2. In the release() method, refcount is decremented and then successfully checked for being 1. As a consequence, the underlying data is released. To prevent this, we test for a self-assignment

fix should be applyed for every window interface and generation

(cherry picked from commit b2790973)
(cherry picked from commit f8758da2)

(cherry picked from commit e650d87e)
(cherry picked from commit ca9c52ac)

Fixed a memory leak in cap_dshow.cpp in videoInput::setVideoSettingCamera(). The leak was caused by not releasing an IBaseFilter object created in a call to getDevice(). Tho object is now properly released.