proxies for FTP urls.

fixed some AC_SUBST configure entries.

Removed and fixed some AC_SUBST configure entries.

to the specific tracker entries

it. This caused a segfault in some fprintf() implementations. Like on Solaris.

- Bug report #1792649 (http://curl.haxx.se/bug/view.cgi?id=1792649) pointed
  out a problem with doing an empty upload over FTP on a re-used connection.
  I added test case 541 to reproduce it and to verify the fix.

- I noticed while writing test 541 that the FTP code wrongly did a CWD on the
  second transfer as it didn't store and remember the "" path from the
  previous transfer so it would instead CWD to the entry path as stored. This
  worked, but did a superfluous command. Thus, test case 541 now also verifies
  this fix.

  second transfer as it didn't store and remember the "" path from the
  previous transfer so it would instead CWD to the entry path as stored. This
  worked, but did a superfluous command. Thus, test case 541 now also verifies
  this fix.

  out a problem with doing an empty upload over FTP on a re-used connection.
  I added test case 541 to reproduce it and to verify the fix.

not success.

(to validate bug #1790403).

sockets.

underlying ftp_readresp() function has a separate "cache" where there might
in fact be leftover data...

sockets.

Renamed the curl_ftpssl enum to curl_usessl and its enumerated constants,
creating macros for backward compatibility.

generic, and more consistent with each other.

case 615 to test an SFTP upload failure.

and allow reuse by multiple protocols. Several unused error codes were
removed.  In all cases, macros were added to preserve source (and binary)
compatibility with the old names.  These macros are subject to removal at
a future date, but probably not before 2009.  An application can be
tested to see if it is using any obsolete code by compiling it with the
CURL_NO_OLDIES macro defined.

Documented some newer error codes in libcurl-error(3)