patch 8.1.0949: MS-windows defines GUI macros different than other systems

Problem:    MS-windows defines GUI macros different than other systems.
Solution:   Swap FEAT_GUI and FEAT_GUI_MSWIN. (Hirohito Higashi, closes #3996)
diff --git a/src/if_ole.cpp b/src/if_ole.cpp
index 8ee348d..8780847 100644
--- a/src/if_ole.cpp
+++ b/src/if_ole.cpp
@@ -6,7 +6,7 @@
  * Do ":help credits" in Vim to see a list of people who contributed.
  */
 
-#if defined(FEAT_OLE) && defined(WIN32) && defined(FEAT_GUI)
+#if defined(FEAT_OLE) && defined(FEAT_GUI_MSWIN)
 /*
  * OLE server implementation.
  *