VCS: Show message box on timeouts/Add SSH prompt.

- Use message boxes on timeouts.
- Add a configuration for a graphical SSH password prompt binary with
defaults
- Launch commands that require authentification with no terminal on UNIX
and environment variable SSH_ASKPASS set accordingly.
- First attempt at introduce a common function to synchronously run VCS
commands in base plugin with flags.
- Use standard execution log entries in all VCS plugins (outputwindow).

src/plugins/cvs/cvsplugin.h

@@ -133,8 +133,7 @@ private:
     CVSResponse runCVS(const QString &workingDirectory,
                        const QStringList &arguments,
                        int timeOut,
-                       bool showStdOutInOutputWindow, QTextCodec *outputCodec = 0,
-                       bool mergeStderr = false);
+                       unsigned flags, QTextCodec *outputCodec = 0);
 
     void annotate(const QString &workingDir, const QString &file,
                   const QString &revision = QString(), int lineNumber= -1);