Match OVERLAPPED structure to the SDK definition.

diff --git a/include/wininet.h b/include/wininet.h
index 8127d40..31b1562 100644
--- a/include/wininet.h
+++ b/include/wininet.h
@@ -1366,7 +1366,7 @@
     union {
       DWORD dwReserved;
       DWORD dwExemptDelta;
-    } u;
+    } DUMMYUNIONNAME;
 } INTERNET_CACHE_ENTRY_INFOA,* LPINTERNET_CACHE_ENTRY_INFOA;
 
 typedef struct _INTERNET_CACHE_ENTRY_INFOW {
@@ -1389,7 +1389,7 @@
     union {
       DWORD dwReserved;
       DWORD dwExemptDelta;
-    } u;
+    } DUMMYUNIONNAME;
 } INTERNET_CACHE_ENTRY_INFOW,* LPINTERNET_CACHE_ENTRY_INFOW;
 
 DECL_WINELIB_TYPE_AW(INTERNET_CACHE_ENTRY_INFO)