Update libssh to (upstream) 0.5.4 == (our) 0.54.

(We need to keep the old numbering syntax to make versions compare
correctly.)

There are only two consumers in pkgsrc; one of them (remmina and
remmina-plugins) actually needed library version 0.4 or later, and
didn't build the ssh/sftp/nx plugins without. Hydra is also supposed
to build with 0.4.x and later.)

Upstream changelogs:

0.5.4:
	CVE-2013-0176 - NULL dereference leads to denial of service
	Fixed several NULL pointer dereferences in SSHv1.
	Fixed a free crash bug in options parsing.

and for completeness 0.5.3:

	This is an important SECURITY and maintenance release in
	order to address CVE-2012-4559, CVE-2012-4560, CVE-2012-4561
	and CVE-2012-4562.

	CVE-2012-4559 - Fix multiple double free() flaws
	CVE-2012-4560 - Fix multiple buffer overflow flaws
	CVE-2012-4561 - Fix multiple invalid free() flaws
	CVE-2012-4562 - Fix multiple improper overflow checks

	(...)

1 files changed, 4 insertions, 8 deletions

diff --git a/security/libssh/DESCR b/security/libssh/DESCR
index c2efacd7512..8c57af67694 100644
--- a/security/libssh/DESCR
+++ b/security/libssh/DESCR
@@ -1,8 +1,4 @@
-The ssh library was designed to be used by programmers needing a working
-SSH implementation by the means of a library. The complete control of the
-client is made by the programmer.
-
-With libssh, you can remotely execute programs, transfer files, use a
-secure and transparent tunnel for your remote programs. With its Secure
-FTP implementation, you can play with remote files easily, without
-third-party programs others than libcrypto (from openssl).
+libssh is a mulitplatform C library implementing the SSHv2 and SSHv1 protocol
+on client and server side. With libssh, you can remotely execute programs,
+transfer files, use a secure and transparent tunnel for
+your remote applications.