patch 8.1.2368: using old C style comments

Problem:    Using old C style comments.
Solution:   Use // comments where appropriate.
diff --git a/src/cindent.c b/src/cindent.c
index c37682c..c7caed6 100644
--- a/src/cindent.c
+++ b/src/cindent.c
@@ -1628,9 +1628,9 @@
  * Ignore a '{' that is in a comment, makes indenting the next three lines
  * work.
  */
-/* foo()    */
-/* {	    */
-/* }	    */
+// foo()
+// {
+// }
 
     static pos_T *
 find_start_brace(void)	    // XXX