Changed FTPD.

[Sergei Organov]

Hello,

I've finished a bunch of changes to the RTEMS FTP server. If the changes seem
to be promising, I'll be glad to submit them to RTEMS maintainers.

Here is the list of changes:

- use pool of pre-created threads to handle sessions instead of
  creating/deleting threads on the fly
- LIST output is now similar to what "/bin/ls -al" would output, thus
  FTP clients such Netscape are happy with it.
- LIST NAME now works (both for files and directories)
- added support for NLST, CDUP, and MDTM FTP commands to make more FTP clients
  happy 
- keep track of CWD for every session separately
- ability to specify root directory name for FTPD in configuration table. FTPD
  will then create illusion for FTP clients that this is actually root
  directory.
- ignore options sent in commands, thus LIST -al FILE works and doesn't try to
  list "-al" directory.
- buffers are allocated on stack instead of heap where possible to eliminate
  malloc/free calls (avoid possible heap fragmentation troubles).
- drop using of task notepad to pass parameters - use function arguments
  instead
- use snprintf() instead of sprintf() everywhere as the latter is unsafe
- use of PF_INET in socket() instead of AF_INET

Here are ftp clients I've tried new FTPD with
(all of them running on Debian GNU/Linux 2.2):

Lftp 2.1.10
NcFTP 2.4.3
Netscape 4.75
ftp
mc 4.5.49

BR,
Sergei Organov.