Fix bug when enter 4 channel image to LineAA function.

https://bugs.launchpad.net/ubuntu/+source/gcc-4.9/+bug/1474304

https://github.com/Itseez/opencv/issues/4791

- IPP is disabled by default when compiler is mingw (couldn't make it
work)
- fixed some warnings
- fixed some `__GNUC__` version checks (for correctness and convenience)
- removed UTF-8 BOM from hough.cpp (fixes #5253)

TODO: Make nosse ver faster than Sobel
      Make sse ver faster than Sobel for BORDER_REPLICATE

TODO: HAL-accelerated code

number

Some code style corrections;

gaussianBlur with CV_32F. hence rouding error are avoided

Removed IPP port for tiny arithm.cpp functions

Additional warnings fix on various platforms.

Build without OPENCL and GCC warnings fixed

Fixed warnings, trailing spaces and removed unused secure_cpy.

IPP code refactored.

IPP code path  implemented as separate static functions to simplify future work with IPP code and make it more readable.

The inner loop of the backward scan got the wrong initial "a".

improvements in Haar CascadeClassifier: 1) use CV_32S instead of CV_32F for the integral of squares (which is more accurate and more efficient); 2) skip the window if its contrast is too low

Signed-off-by: Zhigang Gong <zhigang.gong@intel.com>