When compiling with cmake using -DCMAKE_CXX_STANDARD=11 use `-std=gnu++11`
for PCH compiler flags, otherwise it triggers an error:

   opencv_core_Release.gch: not used because `__cplusplus' defined as ` 201103L' not ` 199711L' [-Winvalid-pch]

Use CXX_EXTENSIONS property to select `gnu++11` or `c++11`.
Trying to mimic cmake logic here: https://gitlab.kitware.com/cmake/cmake/blob/master/Source/cmLocalGenerator.cxx#L1527-1557

v2: fix stray trailing whitespace

v3: only allow for up to one property window at the time

Opening multiple windows in the same process will just confuse
the camera filter or outright crash.

Suggested-by: @alalek

Also return whether a dialog was opened at the time.

* UMat blobs are wrapped

* Replace getUMat and getMat at OpenCLBackendWrapper

* Update to properly find the compiler tools for MSVC 2017

* FindCUDA: Fix the MSVC 2017 compiler tool locations

Signed-off-by: Li Peng <peng.li@intel.com>

Save video file (#10502)

replaces REUSE_DNN_MEMORY compile-time option

Bitwise "and false" is always false.

* Add a parameter labels to command line

* default value

* samples: caffe_googlenet.cpp minor refactoring