Debugger: Code cosmetics

Sprinkling in const and ranged for.

Change-Id: I5d11d57f64140021397c23734c7373544ebebb6f
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/debugger/stackhandler.cpp

@@ -361,7 +361,7 @@ void StackHandler::saveTaskFile()
     }
 
     QTextStream str(&file);
-    foreach (const StackFrame &frame, frames()) {
+    for (const StackFrame &frame : frames()) {
         if (frame.isUsable())
             str << frame.file << '\t' << frame.line << "\tstack\tFrame #" << frame.level << '\n';
     }