On CMake (version 3.1.1 on OS X Yosemite), the variables set by different packages using
find_package seem to follow different conventions.
find_package(OpenGL), the variables
OPENGL_INCLUDE_DIR get set (case-sensitive).
find_package(OpenCV), variables with those names remain empty, but
OpenCV_LIBS get set.
What is the right convention, and is there a way to force CMake to use it, on any platform?