Contribs: fix ssh2 .pc file with zlib

(cherry picked from commit 0d70f5f4b78248c04c2efbc744cc04e2d64b1ac6)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

contrib/src/ssh2/configure-zlib.patch

+--- ssh2/configure.ac	2015-02-24 10:09:30.662277334 +0100
++++ ssh2/configure.ac.new	2015-02-24 10:08:57.658394756 +0100
+@@ -133,6 +133,7 @@
+     AC_MSG_NOTICE([Try --with-libz-prefix=PATH if you know you have it])
+   else
+     AC_DEFINE(LIBSSH2_HAVE_ZLIB, 1, [Compile in zlib support])
++    LIBS="$LIBS -lz"
+   fi
+ fi
+ 

contrib/src/ssh2/rules.mak

@@ -18,6 +18,7 @@ $(TARBALLS)/libssh2-$(LIBSSH2_VERSION).tar.gz:
 ssh2: libssh2-$(LIBSSH2_VERSION).tar.gz .sum-ssh2
 	$(UNPACK)
 	$(APPLY) $(SRC)/ssh2/no-tests.patch
+	$(APPLY) $(SRC)/ssh2/configure-zlib.patch
 	$(MOVE)
 
 DEPS_ssh2 = gcrypt $(DEPS_gcrypt)