cogl: Use COGL_EXPORT to export and install cogl-trace.h
Just like libmutter-clutter, and libmutter, mark exported symbols with an COGL_EXPORT macro. This removes the .map and .map.in files previously used, containing a list of semi private symbols. This symbol was out of date, i.e. pointed to non-existing symbols, and was also replaced with COGL_EXPORT macros.
unit_test_* symbols are exported by the help of the unit test defining macro. test_* symbols are no longer supported as it proved unnecessary.