Use https URLs for links that support it.

README

@@ -5,7 +5,7 @@ instructions and note that we do not use Github for bug reporting or
 patch/pull-request management.
 
 - A Japanese translation of this document and of the release notes is
-- available at http://www.unixuser.org/~haruyama/security/openssh/index.html
+- available at https://www.unixuser.org/~haruyama/security/openssh/index.html
 - Thanks to HARUYAMA Seigo <[email protected]>
 
 This is the port of OpenBSD's excellent OpenSSH[0] to Linux and other
@@ -57,10 +57,10 @@ References -
 [0] https://www.openssh.com/
 [1] http://www.lothar.com/tech/crypto/
 [2] http://prngd.sourceforge.net/
-[3] http://www.gzip.org/zlib/
-[4] http://www.openssl.org/
-[5] http://www.openpam.org
-    http://www.kernel.org/pub/linux/libs/pam/
+[3] https://www.zlib.net/
+[4] https://www.openssl.org/
+[5] https://www.openpam.org
+    https://www.kernel.org/pub/linux/libs/pam/
     (PAM also is standard on Solaris and HP-UX 11)
-[6] http://thrysoee.dk/editline/ (portable version)
-[7] http://man.openbsd.org/style.9
+[6] https://thrysoee.dk/editline/ (portable version)
+[7] https://man.openbsd.org/style.9