[0.4.9] cherry-pick [SYSSETUP] Fix a DPH report about dwPageCount

- "(sdk/lib/rtl/heappage.c:1329) corrupted suffix pattern"
  detected at
  "dll/win32/syssetup/wizard.c:2672 (InstallWizard)"
- Add an ASSERT(), as hinted by Mark Jansen.

(cherry picked from commit 1668527)

Author: SergeGautherie

dll/win32/syssetup/wizard.c

@@ -2503,7 +2503,7 @@ InstallWizard(VOID)
     PSETUPDATA pSetupData = NULL;
     HMODULE hNetShell = NULL;
     PFNREQUESTWIZARDPAGES pfn = NULL;
-    DWORD dwPageCount = 8, dwNetworkPageCount = 0;
+    DWORD dwPageCount = 9, dwNetworkPageCount = 0;
 
     LogItem(L"BEGIN_SECTION", L"InstallWizard");
 
@@ -2636,6 +2636,8 @@ InstallWizard(VOID)
     psp.pszTemplate = MAKEINTRESOURCE(IDD_FINISHPAGE);
     phpage[nPages++] = CreatePropertySheetPage(&psp);
 
+    ASSERT(nPages == dwPageCount);
+
     /* Create the property sheet */
     psh.dwSize = sizeof(PROPSHEETHEADER);
     psh.dwFlags = PSH_WIZARD97 | PSH_WATERMARK | PSH_HEADER | PSH_MODELESS;