[SHELL32][SDK] Implement LinkWindow_RegisterClass (#8878)

Implementing missing features...
JIRA issue: CORE-19278
- Implement LinkWindow_RegisterClass
  function by using "superclassing".
- Add prototype to <undocshell.h>.

dll/win32/shell32/utils.cpp

@@ -2189,3 +2189,31 @@ SHELL32_AliasTranslatePidl(
 {
     return SHELL32_ReparentAsAliasPidl(NULL, NULL, pidl, ppidlNew, dwFlags) ? S_OK : E_FAIL;
 }
+
+/*************************************************************************
+ *              LinkWindow_RegisterClass (SHELL32.258)
+ *
+ * https://learn.microsoft.com/en-us/windows/win32/shell/linkwindow-registerclass
+ */
+EXTERN_C BOOL WINAPI LinkWindow_RegisterClass(VOID)
+{
+    INITCOMMONCONTROLSEX iccx = { sizeof(iccx), ICC_LINK_CLASS };
+    InitCommonControlsEx(&iccx);
+
+    WNDCLASSEXW wcx = { sizeof(wcx) };
+    if (!GetClassInfoExW(NULL, L"SysLink", &wcx))
+        return FALSE;
+
+    /* Superclassing! */
+    wcx.lpszClassName = L"Link Window";
+    return RegisterClassExW(&wcx) || (GetLastError() == ERROR_CLASS_ALREADY_EXISTS);
+}
+
+/*************************************************************************
+ *              LinkWindow_UnregisterClass (SHELL32.259)
+ */
+EXTERN_C BOOL WINAPI LinkWindow_UnregisterClass(_In_ DWORD dwUnused)
+{
+    /* Do nothing. This is correct. */
+    return TRUE;
+}

dll/win32/shell32/wine/shellord.c

@@ -2640,6 +2640,7 @@ HRESULT WINAPI SHSetLocalizedName(LPCWSTR pszPath, LPCWSTR pszResModule, int ids
     return S_OK;
 }
 
+#ifndef __REACTOS__ // See ../utils.cpp
 /*************************************************************************
  *              LinkWindow_RegisterClass (SHELL32.258)
  */
@@ -2657,6 +2658,7 @@ BOOL WINAPI LinkWindow_UnregisterClass(DWORD dwUnused)
     FIXME("()\n");
     return TRUE;
 }
+#endif
 
 /*************************************************************************
  *              SHFlushSFCache (SHELL32.526)

sdk/include/reactos/undocshell.h

@@ -910,6 +910,9 @@ Activate_RunDLL(
 
 BOOL WINAPI SHSettingsChanged(LPCVOID unused, LPCWSTR pszKey);
 
+BOOL WINAPI LinkWindow_RegisterClass(VOID);
+BOOL WINAPI LinkWindow_UnregisterClass(_In_ DWORD dwUnused);
+
 /*****************************************************************************
  * Shell32 resources
  */