bug#767: 23.0.60; compilation-start gives bad default-directory

[Chong Yidong]

> If on w32 default-directory is something like c:\top\sub then the
> subprocess started by compilation-start will get pwd=c:\top.

Does the following patch fix this?

*** trunk/src/callproc.c.~1.240.~       2008-07-31 12:19:14.000000000 -0400
--- trunk/src/callproc.c        2008-08-26 18:15:59.000000000 -0400
***************
*** 374,379 ****
--- 374,381 ----
         a sensible default. */
        current_dir = build_string ("~/");
      current_dir = expand_and_dir_to_file (current_dir, Qnil);
+     current_dir = Ffile_name_as_directory (current_dir);
+ 
      if (NILP (Ffile_accessible_directory_p (current_dir)))
        report_file_error ("Setting current directory",
                         Fcons (current_buffer->directory, Qnil));