patch 8.1.0999: use register one too often and not properly tested

Problem:    Use register one too often and not properly tested.
Solution:   Do not always use register one when specifying a register.
            (closes #4085)  Add more tests.
diff --git a/src/version.c b/src/version.c
index e57b576..e427ffe 100644
--- a/src/version.c
+++ b/src/version.c
@@ -780,6 +780,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    999,
+/**/
     998,
 /**/
     997,