The `codec_tag` is only available when opening a file from disk. If `AVStream` is a network stream then `fourcc` must be obtained using `codec_id`. I have tested the following scenarios:
1) Open a `.mp4` file and verify that `codec_tag` is returned (old behavior)
2) Open a `rtsp` stream and verify that `codec_fourcc` is returned (Tested with a MJPEG, H264 and H265 stream)

TS: fix Python v2/v3 compatibility (#12667)

* TS: fix Python2.7 compatibility

* TS: fix Python3 compatibility

* py3: use integer division '/' => '//' instead of cast

  especially if it matches the module being tested

  * follow the implementation of Luv2RGBfloat in imgproc/src/color_lab.cpp
  * loosen threshold in cudaimgproc

'mFramesCouner' -> 'mFramesCounter'

The regex was only parsing for a single digit in the major version, causing Xcode 10 to be treated as version "1". Other parts of the script only turn on bitcode generation if the Xcode version is > 7.

Fixes for instrumentation of IPP and OCL (#12637)

* fixed warning about re-declaring variable when both IPP and instrumentation are enabled

* fixed segfault when no funName provided

* compilation fixed when both OCL and instrumentation are enabled

* dnn(ocl4dnn): update kernel checks

* dnn: workaround for IDLF kernels on Intel iGPU

* dnn(test): remove "skip" check for unstable cases

* cmake: js cleanup

- avoid unnecessary 2 messages for other platforms
- drop MODULE_NAME variable

* js: cleanup build_js.py

* Remove isIntel check from deep learning layers

* Remove fp16->fp32 fallbacks where it's not necessary

* Fix Kernel::run to prevent localsize > globalsize

* Fix #12542

* Remove ignore of non-virtual-dtor error