patch 8.1.0051: MS-Windows: missing #endif

Problem:    MS-Windows: missing #endif.
Solution:   Add the #endif.
diff --git a/src/os_win32.c b/src/os_win32.c
index f340949..bece2c4 100644
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -5322,6 +5322,7 @@
 #  endif
 	}
     }
+# endif
 }
 
     void