V4 Debugger: Use changebreakpoint command if available

Newer versions of QML will support proper changing of break points, we
won't need to work around it anymore.

Task-number: QTCREATORBUG-20795
Change-Id: Idb5aaeb8ea59c7d2fd7c924e336ea259d3573d3d
Reviewed-by: hjk <hjk@qt.io>

src/plugins/debugger/qml/qmlv8debuggerclientconstants.h

@@ -73,6 +73,7 @@ const char SCOPE[] = "scope";
 const char SCRIPTS[] = "scripts";
 const char SETBREAKPOINT[] = "setbreakpoint";
 const char CLEARBREAKPOINT[] = "clearbreakpoint";
+const char CHANGEBREAKPOINT[] = "changebreakpoint";
 const char SETEXCEPTIONBREAK[] = "setexceptionbreak";
 const char VERSION[] = "version";
 const char DISCONNECT[] = "disconnect";