patch 8.2.3975: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/if_xcmdsrv.c b/src/if_xcmdsrv.c
index 25f63de..6e653c5 100644
--- a/src/if_xcmdsrv.c
+++ b/src/if_xcmdsrv.c
@@ -456,7 +456,7 @@
     vim_free(property);
     if (res < 0)
     {
-	emsg(_("E248: Failed to send command to the destination program"));
+	emsg(_(e_failed_to_send_command_to_destination_program));
 	return -1;
     }
 
@@ -1089,7 +1089,7 @@
 	    XFree(*regPropp);
 	XDeleteProperty(dpy, RootWindow(dpy, 0), registryProperty);
 	if (domsg)
-	    emsg(_("E251: VIM instance registry property is badly formed.  Deleted!"));
+	    emsg(_(e_vim_instance_registry_property_is_badly_formed_deleted));
 	return FAIL;
     }
     return OK;