At least Clang trunk towards 3.4 now rejects incompatible declarations of the
same extern "C" function in different namespaces, so that trick of getting at
the function that is exported by libstdc++ but only rudimentarily if at all
exposed in cxxabi.h no longer worked.

TODO: This change should be reflected in any other bridges where it is relevant,
too.

Change-Id: Ie3ccbdb7d75cc98636d02c0435958532620724f2