openssh: security bump to version 7.6p1

Fixes CVE-2017-15906 - The process_open function in sftp-server.c in OpenSSH
before 7.6 does not properly prevent write operations in readonly mode,
which allows attackers to create zero-length files.

For more details, see the release notes:
https://www.openssh.com/txt/release-7.6

Also add a hash for the license file while we're at it.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/openssh/openssh.hash

@@ -1,2 +1,4 @@
-# From http://www.openssh.com/txt/release-7.5 (base64 encoded)
-sha256 9846e3c5fab9f0547400b4d2c017992f914222b3fd1f8eee6c7dc6bc5e59f9f0  openssh-7.5p1.tar.gz
+# From http://www.openssh.com/txt/release-7.6 (base64 encoded)
+sha256 a323caeeddfe145baaa0db16e98d784b1fbc7dd436a6bf1f479dfd5cd1d21723  openssh-7.6p1.tar.gz
+# Locally calculated
+sha256 05a4c25ef464e19656c5259bd4f4da8428efab01044f3541b79fbb3ff209350f  LICENCE

package/openssh/openssh.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-OPENSSH_VERSION = 7.5p1
+OPENSSH_VERSION = 7.6p1
 OPENSSH_SITE = http://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable
 OPENSSH_LICENSE = BSD-3-Clause, BSD-2-Clause, Public Domain
 OPENSSH_LICENSE_FILES = LICENCE