patch 8.0.0294: argument list is not stored correctly in a session file

Problem:    Argument list is not stored correctly in a session file.
            (lgpasquale)
Solution:   Use "$argadd" instead of "argadd". (closes #1434)
diff --git a/src/version.c b/src/version.c
index 0a5e3d3..4a796bf 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    294,
+/**/
     293,
 /**/
     292,