Put "4" back in; others depend on it (e.g. `ipykernel`)

IPython/lib/guisupport.py

@@ -109,7 +109,7 b' def start_event_loop_wx(app=None):'
 # Qt
 #-----------------------------------------------------------------------------
 
-def get_app_qt(*args, **kwargs):
+def get_app_qt4(*args, **kwargs):
     """Create a new Qt app or return an existing one."""
     from IPython.external.qt_for_kernel import QtGui
     app = QtGui.QApplication.instance()
@@ -119,7 +119,7 b' def get_app_qt(*args, **kwargs):'
         app = QtGui.QApplication(*args, **kwargs)
     return app
 
-def is_event_loop_running_qt(app=None):
+def is_event_loop_running_qt4(app=None):
     """Is the qt event loop running."""
     # New way: check attribute on shell instance
     ip = get_ipython()
@@ -128,18 +128,18 b' def is_event_loop_running_qt(app=None):'
 
     # Old way: check attribute on QApplication singleton
     if app is None:
-        app = get_app_qt([''])
+        app = get_app_qt4([''])
     if hasattr(app, '_in_event_loop'):
         return app._in_event_loop
     else:
         # Does qt provide a other way to detect this?
         return False
 
-def start_event_loop_qt(app=None):
+def start_event_loop_qt4(app=None):
     """Start the qt event loop in a consistent manner."""
     if app is None:
         app = get_app_qt([''])
-    if not is_event_loop_running_qt(app):
+    if not is_event_loop_running_qt4(app):
         app._in_event_loop = True
         app.exec_()
         app._in_event_loop = False