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/watchutils.h

@@ -96,7 +96,7 @@ QString quoteUnprintableLatin1(const QByteArray &ba);
 bool isCppEditor(Core::IEditor *editor);
 QString cppExpressionAt(TextEditor::ITextEditor *editor, int pos,
                         int *line, int *column, QString *function = 0);
-
+QString cppFunctionAt(const QString &fileName, int line);
 // Decode string data as returned by the dumper helpers.
 QString decodeData(const QByteArray &baIn, int encoding);