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

include/llvm/CodeGen/MachinePostDominators.h

@@ -33,7 +33,7 @@ public:
 
   MachinePostDominatorTree();
 
-  ~MachinePostDominatorTree();
+  ~MachinePostDominatorTree() override;
 
   FunctionPass *createMachinePostDominatorTreePass();