patch 9.0.1084: code handling low level MS-Windows events cannot be tested

Problem:    Code handling low level MS-Windows events cannot be tested.
Solution:   Add test_mswin_event() and tests using it. (Christopher Plewright,
            closes #11622)
diff --git a/runtime/doc/usr_41.txt b/runtime/doc/usr_41.txt
index aa51fe3..c67bd99 100644
--- a/runtime/doc/usr_41.txt
+++ b/runtime/doc/usr_41.txt
@@ -1186,6 +1186,7 @@
 	test_getvalue()		get value of an internal variable
 	test_gui_event()	generate a GUI event for testing
 	test_ignore_error()	ignore a specific error message
+	test_mswin_event()	generate an MS-Windows event
 	test_null_blob()	return a null Blob
 	test_null_channel()	return a null Channel
 	test_null_dict()	return a null Dict