emuMB: add EvdevMBEmuOn and call from EvdevOn to register wakeup handlers.

This got broken in b0737bdbd1, when the
EmuMBPreInit call was removed from EvdevOn. As a result, VT switching away and
back wouldn't restore the wakeup handlers and mouse button presses
disappeared.
(cherry picked from commit af096e8c5d)

src/emuMB.c

@@ -317,6 +317,11 @@ EvdevMBEmuPreInit(InputInfoPtr pInfo)
 
     pEvdev->emulateMB.timeout = xf86SetIntOption(pInfo->options,
                                                  "Emulate3Timeout", 50);
+}
+
+void
+EvdevMBEmuOn(InputInfoPtr pInfo)
+{
     RegisterBlockAndWakeupHandlers (EvdevMBEmuBlockHandler,
                                     EvdevMBEmuWakeupHandler,
                                     (pointer)pInfo);

src/evdev.c

@@ -1008,6 +1008,7 @@ EvdevOn(DeviceIntPtr device)
     } else
     {
         xf86AddEnabledDevice(pInfo);
+        EvdevMBEmuOn(pInfo);
         pEvdev->flags |= EVDEV_INITIALIZED;
         device->public.on = TRUE;
     }

src/evdev.h

@@ -127,6 +127,7 @@ BOOL EvdevMBEmuFilterEvent(InputInfoPtr, int, BOOL);
 void EvdevMBEmuWakeupHandler(pointer, int, pointer);
 void EvdevMBEmuBlockHandler(pointer, struct timeval**, pointer);
 void EvdevMBEmuPreInit(InputInfoPtr);
+void EvdevMBEmuOn(InputInfoPtr);
 void EvdevMBEmuFinalize(InputInfoPtr);
 void EvdevMBEmuEnable(InputInfoPtr, BOOL);