patch 9.1.1190: C indentation does not detect multibyte labels

Problem:  C indentation does not detect multibyte labels
Solution: Correctly skip over multibyte characters
          (Anttoni Erkkilä)

closes: #16770

Signed-off-by: Anttoni Erkkilä <anttoni.erkkila@protonmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/cindent.c b/src/cindent.c
index cf18441..2414b3f 100644
--- a/src/cindent.c
+++ b/src/cindent.c
@@ -405,7 +405,12 @@
 	return FALSE;
 
     while (vim_isIDc(**s))
-	(*s)++;
+    {
+        if (has_mbyte)
+            (*s) += (*mb_ptr2len)(*s);
+        else
+            (*s)++;
+    }
 
     *s = cin_skipcomment(*s);