patch 8.2.2922: computing array length is done in various ways

Problem:    Computing array length is done in various ways.
Solution:   Use ARRAY_LENGTH everywhere. (Ken Takata, closes #8305)
diff --git a/src/cindent.c b/src/cindent.c
index b2fac1a..ce02402 100644
--- a/src/cindent.c
+++ b/src/cindent.c
@@ -718,7 +718,7 @@
     {
 	int i, l;
 
-	for (i = 0; i < (int)(sizeof(skip) / sizeof(char *)); ++i)
+	for (i = 0; i < (int)ARRAY_LENGTH(skip); ++i)
 	{
 	    l = (int)strlen(skip[i]);
 	    if (cin_starts_with(s, skip[i]))