commands: Use override instead of virtual.

Summary:
This removes all uses of virtual on functions
where override could be used, including on destructors.

It also adds override where virtual was previously
missing.

Reviewers: clayborg, labath

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D13503

llvm-svn: 249564
diff --git a/lldb/source/Commands/CommandObjectBugreport.cpp b/lldb/source/Commands/CommandObjectBugreport.cpp
index f171d2f..3d00cb8 100644
--- a/lldb/source/Commands/CommandObjectBugreport.cpp
+++ b/lldb/source/Commands/CommandObjectBugreport.cpp
@@ -43,7 +43,7 @@
         m_option_group.Finalize();
     }
 
-    ~CommandObjectBugreportUnwind()
+    ~CommandObjectBugreportUnwind() override
     {
     }