Refactored detecting several Apple-related technologies.

Now the HAVE_* macros are set using cvconfig.h. Previously most
of them already were there, but were always undefined. One,
HAVE_COCOA, I had to add.

This also makes the CMake code more consistent; now, WITH_* variables
are always checked in cmake/*, while HAVE_* variables are checked in
modules/highgui/CMakeLists.txt.

cmake/templates/cvconfig.h.cmake

@@ -16,6 +16,9 @@
 /* Carbon windowing environment */
 #cmakedefine HAVE_CARBON
 
+/* Cocoa API */
+#cmakedefine HAVE_COCOA
+
 /* IEEE1394 capturing support */
 #cmakedefine HAVE_DC1394