Debugger: Add infrastructure for message tracepoints.

Add context menu to add a 'message tracepoint', that is,
a trace point that outputs a user message and continues.
Intended to be a replacement for manually inserting
a qDebug() into the code to understand the call sequence.
Yet to be implemented for gdb.

Change-Id: I1c303001421fbbae74d98d15d52718579350db6e
Rubber-stamped-by: hjk
Reviewed-on: http://codereview.qt.nokia.com/756
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>

src/plugins/debugger/breakpoint.cpp

@@ -207,6 +207,8 @@ BreakpointParts BreakpointParameters::differencesTo
         parts |= ModulePart;
     if (command != rhs.command)
         parts |= CommandPart;
+    if (message != rhs.message)
+        parts |= MessagePart;
     return parts;
 }
 
@@ -275,6 +277,8 @@ QString BreakpointParameters::toString() const
         ts << " Module: " << module;
     if (!command.isEmpty())
         ts << " Command: " << command;
+    if (!message.isEmpty())
+        ts << " Message: " << message;
     return result;
 }