opencv: Fixup include to follow new standard

opencv: Fixup include to follow new standard

This uses the new path for OpenCV headers. OpenCV now have
master headers files per modules, which reduce the amount of
required includes. Note that HIGHGUI was included to get the
imgcodecs includes, which I fixed, though the master header is
missing the C headers, so I included that directly. All the
image stuff should be ported to C++ eventually. Finally, this
patch also update the header checks to reflect the modules that
are really being used.