objectiveC++: When throwing c++ exception of

objectiveC++: When throwing c++ exception of
an objectiveC object, use objc_exception_throw
to raise the exception. // rdar://12605907

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172091 91177308-0d34-0410-b5e6-96231b3b80d8