patch 8.2.4005: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/gui_w32.c b/src/gui_w32.c
index e612505..cba3179 100644
--- a/src/gui_w32.c
+++ b/src/gui_w32.c
@@ -4965,7 +4965,7 @@
     EnumWindows(FindWindowTitle, (LPARAM)title);
     if (vim_parent_hwnd == NULL)
     {
-	semsg(_("E671: Cannot find window title \"%s\""), title);
+	semsg(_(e_cannot_find_window_title_str), title);
 	mch_exit(2);
     }
 }
@@ -5303,7 +5303,7 @@
 #endif
 	if (s_hwnd == NULL)
 	{
-	    emsg(_("E672: Unable to open window inside MDI application"));
+	    emsg(_(e_unable_to_open_window_inside_mdi_application));
 	    mch_exit(2);
 	}
     }