new VFS directory listing parser

[Roland Illig <roland illig gmx de>]

The current directory listing parser (for ftpfs and extfs) has problems 
with file names starting with white-space or a four-digit sequence.

Today I have completely rewritten the parser code. The file vfsparse.h 
in the patch contains a lot of parsing functions that can be used not 
only in the vfs part, but also as stand-alone functions. They contain a 
simple-to-use, common interface that makes it easy to combine the 
functions to parse bigger blocks (see vfs_parse_unix_line for an example).

I have tested the patched code on some servers, and it worked fine. I 
haven't yet tested the MS-DOS-style listing code, as I haven't found any 
FTP server providing that type of listing. I also haven't found any FTP 
server that doesn't include the `group' column in its output.

If you know of any weird FTP servers that are not handled by this code, 
please tell me.

Roland