patch 8.2.4003: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/gui_at_fs.c b/src/gui_at_fs.c
index 5011449..739d309 100644
--- a/src/gui_at_fs.c
+++ b/src/gui_at_fs.c
@@ -1066,7 +1066,7 @@
 #endif
 	if (!SFfont)
 	{
-	    semsg(_("E616: vim_SelFile: can't get font %s"), SF_DEFAULT_FONT);
+	    semsg(_(e_vim_selfile_cant_get_font_str), SF_DEFAULT_FONT);
 	    SFstatus = SEL_FILE_CANCEL;
 	    return;
 	}
@@ -2648,7 +2648,7 @@
     XtRemoveTimeOut(SFdirModTimerId);
     if (SFchdir(SFstartDir))
     {
-	emsg(_("E614: vim_SelFile: can't return to current directory"));
+	emsg(_(e_vim_selfile_cant_return_to_current_directory));
 	SFstatus = SEL_FILE_CANCEL;
     }
 }
@@ -2677,7 +2677,7 @@
 
     if (mch_dirname((char_u *)SFstartDir, MAXPATHL) == FAIL)
     {
-	emsg(_("E615: vim_SelFile: can't get current directory"));
+	emsg(_(e_vim_selfile_cant_get_current_directory));
 	return NULL;
     }