patch 8.1.1248: no test for dec mouse

Problem:    No test for dec mouse.
Solution:   Add some tests for dec mouse.  Add "no_query_mouse".
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index f728c12..8faf17f 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -9805,6 +9805,8 @@
 		starting     reset the "starting" variable, see below
 		nfa_fail     makes the NFA regexp engine fail to force a
 			     fallback to the old engine
+		no_query_mouse  do not query the mouse position for "dec"
+				terminals
 		ALL	     clear all overrides ({val} is not used)
 
 		"starting" is to be used when a test should behave like