Use 'override/final' instead of 'virtual' for overridden methods

The patch is generated using clang-tidy misc-use-override check.

This command was used:

  tools/clang/tools/extra/clang-tidy/tool/run-clang-tidy.py \
    -checks='-*,misc-use-override' -header-filter='llvm|clang' \
    -j=32 -fix -format

http://reviews.llvm.org/D8925



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234679 91177308-0d34-0410-b5e6-96231b3b80d8

examples/ExceptionDemo/ExceptionDemo.cpp

@@ -1573,7 +1573,7 @@ public:
                                  std::runtime_error::operator=(toCopy)));
   }
 
-  virtual ~OurCppRunException (void) throw () {}
+  ~OurCppRunException(void) throw() override {}
 };
 } // end anonymous namespace