patch 8.0.1504: Win32: the screen may be cleared on startup

Problem:    Win32: the screen may be cleared on startup.
Solution:   Only call shell_resized() when the size actually changed. (Ken
            Takata, closes #2527)
diff --git a/src/version.c b/src/version.c
index 5c72d8d..968f1e0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -772,6 +772,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1504,
+/**/
     1503,
 /**/
     1502,