...by adding some further SAL_DLLPUBLIC_RTTI type annotations (cf.
b4f6b26b "SAL_DLLPUBLIC_RTTI for proper RTTI
visibility for LLVM") and by making sure relevant function types do not use
incomplete types in their parameter and return types (which would make the RTTI
hidden).

Change-Id: Id7aadcbc0704b9759968ae36266fc9ce11a2e340