minui: add ev_get_epollfd() to retrieve epoll file descriptor

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

Change-Id: If73717b64d7c455ca726b90a815a31c1edf52544
diff --git a/minui/events.c b/minui/events.c
index fe364bf..008a7d8 100644
--- a/minui/events.c
+++ b/minui/events.c
@@ -132,6 +132,11 @@
     return ret;
 }
 
+int ev_get_epollfd(void)
+{
+    return epollfd;
+}
+
 void ev_exit(void)
 {
     while (ev_count > 0) {
diff --git a/minui/minui.h b/minui/minui.h
index 805c58b..ab08202 100644
--- a/minui/minui.h
+++ b/minui/minui.h
@@ -67,6 +67,7 @@
 
 int ev_get_input(int fd, unsigned int epevents, struct input_event *ev);
 void ev_dispatch(void);
+int ev_get_epollfd(void);
 
 // Resources