it tries to remove 'opencv_' prefix from 'name' variable, but
it creates new variable with the same name as module

- Previous version just checked option support, but not enable it.
- Also OpenCV tests reports invalid AVX and AVX2 support status.

"int * CvMLData::sample_idx" was not freed

use ASSERT_FLOAT_EQ to compare float values, it is more robust for
large values

* cmake CMP0054 and CMP0045
* aarch64 build
* portable code options in PCH cmake
* some of gcc 4.9 warnings

... before any exceptions occur.

highgui: Support to change trackbar count in setTrackbarPos and replaced deprecated CreateToolbarEx in Windows.