patch 8.1.0677: look-behind match may use the wrong line number

Problem:    Look-behind match may use the wrong line number. (Dominique Pelle)
Solution:   Use the line number in regsave instead of the one in behind_pos,
            we may be looking at the previous line. (closes #3749)
diff --git a/src/version.c b/src/version.c
index 53dda7f..439e1bc 100644
--- a/src/version.c
+++ b/src/version.c
@@ -800,6 +800,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    677,
+/**/
     676,
 /**/
     675,