patch 8.1.1376: warnings for size_t/int mixups

Problem:    Warnings for size_t/int mixups.
Solution:   Change types, add type casts. (Mike Williams)
diff --git a/src/search.c b/src/search.c
index 2bcbf0a..e57c101 100644
--- a/src/search.c
+++ b/src/search.c
@@ -4990,7 +4990,7 @@
     if (cur > 0)
     {
 	char	t[SEARCH_STAT_BUF_LEN] = "";
-	int	len;
+	size_t	len;
 
 #ifdef FEAT_RIGHTLEFT
 	if (curwin->w_p_rl && *curwin->w_p_rlc == 's')