patch 8.1.1647: build error with GTK and hangulinput feature

Problem:    Build error with GTK and hangulinput feature, im_get_status()
            defined twice. (Dominique Pelle)
Solution:   Adjust im_get_status(). (closes #4628)
diff --git a/src/mbyte.c b/src/mbyte.c
index 9c03f08..94adddf 100644
--- a/src/mbyte.c
+++ b/src/mbyte.c
@@ -5848,6 +5848,11 @@
     int
 im_get_status(void)
 {
+#  ifdef FEAT_HANGULIN
+    if (hangul_input_state_get())
+	return TRUE;
+#  endif
+
 #  ifdef FEAT_EVAL
     if (USE_IMSTATUSFUNC)
 	return call_imstatusfunc();