patch 8.0.0254: error message of assert functions is sometimes incomplete

Problem:    When using an assert function one can either specify a message or
            get a message about what failed, not both.
Solution:   Concatenate the error with the message.
diff --git a/src/version.c b/src/version.c
index 19ba72e..e66e1b9 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    254,
+/**/
     253,
 /**/
     252,