minui: add ev_get_epollfd() to retrieve epoll file descriptor

To allow use of ev_* functions with an external main loop.

Change-Id: If73717b64d7c455ca726b90a815a31c1edf52544

minui/events.c

@@ -132,6 +132,11 @@ int ev_add_fd(int fd, ev_callback cb, void *data)
     return ret;
 }
 
+int ev_get_epollfd(void)
+{
+    return epollfd;
+}
+
 void ev_exit(void)
 {
     while (ev_count > 0) {

minui/minui.h

@@ -67,6 +67,7 @@ int ev_wait(int timeout);
 
 int ev_get_input(int fd, unsigned int epevents, struct input_event *ev);
 void ev_dispatch(void);
+int ev_get_epollfd(void);
 
 // Resources