Use wxString::t_str() in calls to Windows API functions in wxMSW.

Use t_str() instead of wx_str() to make the code work correctly in UTF-8 build
in which wx_str() returns a pointer to UTF-8 buffer while we need a wchar_t
pointer for Windows.

Closes #14371.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71640 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/dirdlg.cpp

@@ -263,7 +263,7 @@ int wxDirDialog::ShowSHBrowseForFolder(WXHWND owner)
 #endif
     bi.ulFlags        = BIF_RETURNONLYFSDIRS | BIF_STATUSTEXT;
     bi.lpfn           = BrowseCallbackProc;
-    bi.lParam         = (LPARAM)m_path.wx_str(); // param for the callback
+    bi.lParam         = wxMSW_CONV_LPARAM(m_path); // param for the callback
 
     static const int verComCtl32 = wxApp::GetComCtl32Version();
 
@@ -490,7 +490,7 @@ BrowseCallbackProc(HWND hwnd, UINT uMsg, LPARAM lp, LPARAM pData)
                     }
 
                     SendMessage(hwnd, BFFM_SETSTATUSTEXT,
-                                0, (LPARAM)strDir.wx_str());
+                                0, wxMSW_CONV_LPARAM(strDir));
                 }
             }
             break;