CORRADE_GRACEFUL_ASSERT is set only on files where it makes sense, the
rest is shared between main and test libraries. Speeds up the
compilation like infinity times.
CMake 2.8.8 is required for OBJECT library target.
The unit test was so weak that this parenthesis error wasn't spotted
until now. Updated the unit test to don't accept the previous code and
also floats everywhere instead of ints.