Utils: Fix possible crash in SynchronousProcess

Disconnect before deleting our data: Otherwise we will get called
via our signals again and then access members that were already
deleted.

Task-number: QTCREATORBUG-4361
Reviewed-by: Friedemann Kleint
(cherry picked from commit 72ae03ba80)

src/libs/utils/synchronousprocess.cpp

@@ -251,6 +251,8 @@ SynchronousProcess::SynchronousProcess() :
 
 SynchronousProcess::~SynchronousProcess()
 {
+    disconnect(&m_d->m_timer, 0, this, 0);
+    disconnect(&m_d->m_process, 0, this, 0);
     delete m_d;
 }