242 - SSH knownhost support (powered by libssh2 1.2)

Committed now. Not yet thoroughly degbugged etc, but at least the funtionality
is now present.

TODO-RELEASE

 To be addressed in 7.19.6 (planned release: August 2009)
 =========================
 
-242 - SSH knownhost support (powered by libssh2 1.2)
-
 243 - ftp QUOTE commands that are allowed to fail but not close the connection
 
 244 - patch for [out] parameters