added OpenCVFindIPP.cmake script, which will look for IPP installation at CMake configuration time. First, IPPROOT environment variable will be tested, if not found script will look at default install places.
The script should support IPP from 5.3 up to 7.x versions (although tested on Windows for IPP 6.1 and IPP 7.0 versions only)

Preliminary optimization of HOG with IPP added too. Not yet quite efficient, code for cpu branch should be redesigned in order to have better performance.

do not use WIN64/_WIN64 anymore - CMake did not set it anyway. Use WIN32 + __x86_64 or _M_X64 instead. Also, make VideoInput optional (WITH_VIDEOINPUT=ON/OFF) => now Mingw-dw2 can build OpenCV

added workaround for strange tmpnam() output from VS2010. turned off optimization for DCT & DFT on Win64 for VS200x (VS2010 builds it fine)