[USER32] Refactoring on LoadKeyboardLayout(W/Ex) (#4601)

- Add IntLoadKeyboardLayout (Win: LoadKeyboardLayoutWorker) helper function.
- Use it in LoadKeyboardLayoutW and LoadKeyboardLayoutEx functions.
CORE-11700

win32ss/user/user32/misc/stubs.c

@@ -441,15 +441,6 @@ BOOL WINAPI IsServerSideWindow(HWND wnd)
   return FALSE;
 }
 
-/*
- * @unimplemented
- */
-HKL WINAPI LoadKeyboardLayoutEx(DWORD unknown,LPCWSTR pwszKLID,UINT Flags) //1st parameter unknown
-{
-  UNIMPLEMENTED;
-  return FALSE;
-}
-
 /*
  * @unimplemented
  */

win32ss/user/user32/windows/input.c

@@ -639,11 +639,16 @@ LoadKeyboardLayoutA(LPCSTR pszKLID,
 }
 
 /*
- * @implemented
+ * @unimplemented
  */
-HKL WINAPI
+/* Win: LoadKeyboardLayoutWorker */
-LoadKeyboardLayoutW(LPCWSTR pwszKLID,
+HKL APIENTRY
-                    UINT Flags)
+IntLoadKeyboardLayout(
+    _In_    HKL     hklUnload,
+    _In_z_  LPCWSTR pwszKLID,
+    _In_    LANGID  wLangID,
+    _In_    UINT    Flags,
+    _In_    BOOL    unknown5)
 {
     DWORD dwhkl, dwType, dwSize;
     UNICODE_STRING ustrKbdName;
@@ -712,6 +717,31 @@ LoadKeyboardLayoutW(LPCWSTR pwszKLID,
                                       dwhkl, Flags);
 }
 
+/*
+ * @implemented
+ */
+HKL WINAPI
+LoadKeyboardLayoutW(LPCWSTR pwszKLID,
+                    UINT Flags)
+{
+    TRACE("(%s, 0x%X)", debugstr_w(pwszKLID), Flags);
+    return IntLoadKeyboardLayout(NULL, pwszKLID, 0, Flags, FALSE);
+}
+
+/*
+ * @unimplemented
+ */
+HKL WINAPI
+LoadKeyboardLayoutEx(HKL hklUnload,
+                     LPCWSTR pwszKLID,
+                     UINT Flags)
+{
+    FIXME("(%p, %s, 0x%X)", hklUnload, debugstr_w(pwszKLID), Flags);
+    if (!hklUnload)
+        return NULL;
+    return IntLoadKeyboardLayout(hklUnload, pwszKLID, 0, Flags, FALSE);
+}
+
 /*
  * @implemented
  */