DOS/Windows-specific code: top.c

[Eli Zaretskii]

    * top.c:

    #ifdef __MSDOS__
    void
    do_chdir_cleanup (void *old_dir)
    {
      chdir (old_dir);
      xfree (old_dir);
    }
    #endif

See the next snippet.

    * top.c:gdb_init()
    
    #ifdef __MSDOS__
      /* Make sure we return to the original directory upon exit, come
	 what may, since the OS doesn't do that for us.  */
      make_final_cleanup (do_chdir_cleanup, xstrdup (current_directory));
    #endif

This is the same issue as with cli-cmds.c:shell_escape(), and the same
solution will do here.


    * top.c:init_history()

    #ifdef __MSDOS__
	  /* No leading dots in file names are allowed on MSDOS.  */
	  history_filename = concat (current_directory, "/_gdb_history", NULL);
    #else
	  history_filename = concat (current_directory, "/.gdb_history", NULL);
    #endif
`

Should we have a NO_LEADING_DOTS_IN_FILENAMES macro?