Drop unused variables and lambda captures

Also, add context to connect() expressions where we are or were
capturing "this".

Change-Id: I6e006ba6f83d532478018550d148ee93eca59605
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>
Reviewed-by: hjk <hjk@qt.io>

src/plugins/debugger/stackhandler.cpp

@@ -418,7 +418,7 @@ bool StackHandler::contextMenuEvent(const ItemViewEvent &ev)
                    });
 
         addAction(menu, tr("Disassemble Function..."), true,
-                  [this, address] {
+                  [this] {
                         const StackFrame frame = inputFunctionForDisassembly();
                         if (!frame.function.isEmpty())
                             m_engine->openDisassemblerView(Location(frame));