patch 8.0.0623: error for invalid regexp is not very informative

Problem:    The message "Invalid range" is used for multiple errors.
Solution:   Add two more specific error messages. (Itchyny, Ken Hamada)
diff --git a/src/version.c b/src/version.c
index 0304389..e07d2a8 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    623,
+/**/
     622,
 /**/
     621,