[QT] use alert icon with tooltip insted of "(out of sync)" text

# Conflicts:
#	src/qt/forms/overviewpage.ui
#	src/qt/overviewpage.cpp

src/qt/bitcoin.qrc

@@ -45,6 +45,7 @@
         <file alias="about">res/icons/about.png</file>
         <file alias="about_qt">res/icons/about_qt.png</file>
         <file alias="verify">res/icons/verify.png</file>
+        <file alias="warning">res/icons/warning.png</file>
     </qresource>
     <qresource prefix="/movies">
         <file alias="spinner-000">res/movies/spinner-000.png</file>