Disallow extern decls of type void in C++ mode

C++ and C differ with respect to the handling of extern void
declarations. Enforce the C++ behavior in C++ mode.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182814 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed