Fix "not all control paths return" warning. NFCI.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@354681 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Analysis/AnyCall.h

@@ -173,6 +173,7 @@ public:
     case Deallocator:
       return cast<FunctionDecl>(D)->getReturnType();
     }
+    llvm_unreachable("Unknown AnyCall::Kind");
   }
 
   /// \returns Function identifier if it is a named declaration,