Add a Socket implementation which just holds an error message.

This isn't yet used, but I plan to use it in situations where you have
to report errors by returning a valid Socket on which the client wlil
call sk_socket_error, but in fact you notice the error _before_
instantiating your usual kind of Socket. The resulting Socket is
usable for nothing except reading out the error string and closing it.

[originally from svn r10065]

Recipe

@@ -300,7 +300,7 @@ SSH      = ssh sshcrc sshdes sshmd5 sshrsa sshrand sshsha sshblowf
          + sshdh sshcrcda sshpubk sshzlib sshdss x11fwd portfwd
          + sshaes sshsh256 sshsh512 sshbn wildcard pinger ssharcf
          + sshgssc pgssapi
-WINSSH   = SSH winnoise winpgntc wingss
+WINSSH   = SSH winnoise winpgntc wingss errsock
 UXSSH    = SSH uxnoise uxagentc uxgss
 
 # SFTP implementation (pscp, psftp).
@@ -310,7 +310,7 @@ SFTP     = sftp int64 logging
 # Pageant or PuTTYgen).
 MISC     = timing callback misc version settings tree234 proxy conf
 WINMISC  = MISC winstore winnet winhandl cmdline windefs winmisc winproxy
-         + wintime
+         + wintime errsock
 UXMISC   = MISC uxstore uxsel uxnet cmdline uxmisc uxproxy time
 OSXMISC  = MISC uxstore uxsel osxsel uxnet uxmisc uxproxy time