patch 8.1.0906: using clumsy way to get console window handle

Problem:    Using clumsy way to get console window handle.
Solution:   Use GetConsoleWindow(). (Ken Takata, closes #3940)
diff --git a/src/version.c b/src/version.c
index f28d69d..3a71b93 100644
--- a/src/version.c
+++ b/src/version.c
@@ -784,6 +784,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    906,
+/**/
     905,
 /**/
     904,