patch 8.2.0337: build fails on a few systems

Problem:    Build fails on a few systems.
Solution:   Use vim_snprintf() instead of snprintf().
diff --git a/src/cmdexpand.c b/src/cmdexpand.c
index ece5a46..1f70dc5 100644
--- a/src/cmdexpand.c
+++ b/src/cmdexpand.c
@@ -2124,7 +2124,7 @@
 	int len = (int)STRLEN(pat) + 20;
 
 	tofree = alloc(len);
-	snprintf((char *)tofree, len, "^<SNR>\\d\\+_%s", pat + 3);
+	vim_snprintf((char *)tofree, len, "^<SNR>\\d\\+_%s", pat + 3);
 	pat = tofree;
     }