qt: use series of pngs for spinner

Use a series of .png frames for the spinner instead of a .mng.
`mng` is an obscure image format and is not built by default into Qt5.

This appears to improve the crispness of the spinner as well.

Does not noticably increase the size (still ~27k) and the code
is not more complicated either.

src/qt/bitcoingui.cpp

@@ -39,7 +39,6 @@
 #include <QMenuBar>
 #include <QMessageBox>
 #include <QMimeData>
-#include <QMovie>
 #include <QProgressBar>
 #include <QSettings>
 #include <QStackedWidget>
@@ -68,7 +67,8 @@ BitcoinGUI::BitcoinGUI(bool fIsTestnet, QWidget *parent) :
     trayIcon(0),
     notificator(0),
     rpcConsole(0),
-    prevBlocks(0)
+    prevBlocks(0),
+    spinnerFrame(0)
 {
     GUIUtil::restoreWindowGeometry("nWindow", QSize(850, 550), this);
 
@@ -187,8 +187,6 @@ BitcoinGUI::BitcoinGUI(bool fIsTestnet, QWidget *parent) :
     statusBar()->addWidget(progressBar);
     statusBar()->addPermanentWidget(frameBlocks);
 
-    syncIconMovie = new QMovie(":/movies/update_spinner", "mng", this);
-
     connect(openRPCConsoleAction, SIGNAL(triggered()), rpcConsole, SLOT(show()));
 
     // prevents an oben debug window from becoming stuck/unusable on client shutdown
@@ -684,9 +682,13 @@ void BitcoinGUI::setNumBlocks(int count, int nTotalBlocks)
         progressBar->setVisible(true);
 
         tooltip = tr("Catching up...") + QString("<br>") + tooltip;
-        labelBlocksIcon->setMovie(syncIconMovie);
         if(count != prevBlocks)
-            syncIconMovie->jumpToNextFrame();
+        {
+            labelBlocksIcon->setPixmap(QIcon(QString(
+                ":/movies/spinner-%1").arg(spinnerFrame, 3, 10, QChar('0')))
+                .pixmap(STATUSBAR_ICONSIZE, STATUSBAR_ICONSIZE));
+            spinnerFrame = (spinnerFrame + 1) % SPINNER_FRAMES;
+        }
         prevBlocks = count;
 
 #ifdef ENABLE_WALLET