VCS: Fix time-out handling for synchronous processes.

Introduce static utilities to Utils::SynchronousProcess
for synchronous processes that mimicks the handling
of Utils::SynchronousProcess (apply timeout after no
more data are available on stdout/stderr as opposed
to waitForFinished()).

Task-number: QTCREATORBUG-777

src/plugins/git/gitcommand.h

@@ -71,8 +71,6 @@ public:
     void setTerminationReportMode(TerminationReportMode m);
 
     static QString msgTimeout(int seconds);
-    // Helper to kill a process by SIGNAL first, allowing for cleanup
-    static bool stopProcess(QProcess &p);
 
 private:
     void run();