Two changes: 1) I still didn't have the ABI correct to match the gcc-4.2...

Two changes:  1)  I still didn't have the ABI correct to match the gcc-4.2 std::string under the exception classes.  I think the changes to stdexcept.cpp have got that down now.  2) On Apple platforms I'm seeing visibility bugs in applications with respect to type_info's being hidden.  This is causing dynamic_cast to malfunction because there are multiple type_info's running around for one type within an application, making dynamic_cast believe that one type is actually multiple types.  As a stop gap measure I'm trying to detect this error, print out an error message, but continue with the most likely desired result.  This is all under __APPLE__.  This behavior can be expanded to other platforms if desired.

llvm-svn: 164809