patch 8.0.1666: % argument in ch_log() causes trouble

Problem:    % argument in ch_log() causes trouble.
Solution:   Use string as third argument in internal ch_log(). (Dominique
            Pelle, closes #2784)
diff --git a/src/version.c b/src/version.c
index b29d64c..44fb030 100644
--- a/src/version.c
+++ b/src/version.c
@@ -763,6 +763,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1666,
+/**/
     1665,
 /**/
     1664,