ProjectExplorer: use enum instead of QString for run mode

Change-Id: Ia906944a489b09afdea59f74afbf759b4caebe37
Reviewed-by: Aurindam Jana <aurindam.jana@nokia.com>
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>

src/plugins/valgrind/memchecktool.h

@@ -94,6 +94,7 @@ public:
     MemcheckTool(QObject *parent);
 
     Core::Id id() const;
+    ProjectExplorer::RunMode runMode() const;
     QString displayName() const;
     QString description() const;