Add checkippsupport

Adds a cv::checkIPPSupport() function whit inits IPP and returns true if everything is OK.

But system.cpp still calls ippStaticInit() which apparently is deprecated.

http://software.intel.com/en-us/articles/ipp-dispatcher-control-functions-ippinit-functions

So, perhaps I should convert the IPPInitializer variable to hold the return value of the now recommended ippInit() and expose that publicly instead.