Renaming for consistency's sake

QGCInstaller.pri

@@ -18,7 +18,7 @@
 # -------------------------------------------------
 
 installer {
-    DEFINES += __installer_version__
+    DEFINES += QGC_INSTALL_RELEASE
     MacBuild {
         VideoEnabled {
             # Install the gstreamer framework

src/QGCApplication.cc

@@ -134,7 +134,7 @@ static QObject* mavManagerSingletonFactory(QQmlEngine*, QJSEngine*)
 #if defined(QGC_GST_STREAMING)
 #ifdef Q_OS_MAC
 #ifndef __ios__
-#ifdef __installer_version__
+#ifdef QGC_INSTALL_RELEASE
 static void qgcputenv(const QString& key, const QString& root, const QString& path)
 {
     QString value = root + path;
@@ -282,7 +282,7 @@ QGCApplication::QGCApplication(int &argc, char* argv[], bool unitTesting)
 #if defined(QGC_GST_STREAMING)
 #ifdef Q_OS_MAC
 #ifndef __ios__
-#ifdef __installer_version__
+#ifdef QGC_INSTALL_RELEASE
     QString currentDir = QCoreApplication::applicationDirPath();
     qgcputenv("GST_PLUGIN_SCANNER",           currentDir, "/gst-plugin-scanner");
     qgcputenv("GTK_PATH",                     currentDir, "/../Frameworks/GStreamer.framework/Versions/Current");