CMake: Remove test DEAL_II_HAVE_CXX11_ICCBOOSTSIGNALSBUG_OK

We cannot sanely test for this regression prior to boost setup. And after
boost setup it is incredibly ugly to do so because DEAL_II_WITH_STDCXX11 is
already processed.
CMake: Bugfix: Also sanitize (cpp) macros in enable_if_links
Merge pull request #185 from tamiko/fix_cxx_test

Fix cxx test