Bugfix: SingleApplication passing a copy of argc instead of reference

QApplication uses a reference of argc so it could modify it's value when
it substitutes known arguments for example.

Thanks to @Chocobozzz for reporting the issue.
https://github.com/itay-grudev/SingleApplication/issues/1

singleapplication.cpp

@@ -7,7 +7,7 @@
  * @param argc
  * @param argv
  */
-SingleApplication::SingleApplication(int argc, char *argv[])
+SingleApplication::SingleApplication(int &argc, char *argv[])
     : QApplication(argc, argv)
 {
     QString serverName = QApplication::organizationName() + QApplication::applicationName();

singleapplication.h

@@ -13,7 +13,7 @@ class SingleApplication : public QApplication
 {
   Q_OBJECT
 public:
-  explicit SingleApplication(int, char *[]);
+  explicit SingleApplication(int&, char *[]);
   ~SingleApplication();
 
 signals: