Contribs: update gnuTLS to the latest of the 2.12.x branch

contrib/src/gnutls/SHA512SUMS

-727abef7b38704315dff89d39a7ab91f55ff7615a5958d6b988a03ec6e3701fd4537c8792ada45ae2afb290b23d8dbb009090dab1ae15da27d3b19aefbbf515c  gnutls-2.12.7.tar.bz2
+49fde72d049ca75d3df15744519296a5eb982560d739cf9b41033b758564df59698be857bc86825f1ae2dc71b3479208701482bfc085f22e9ff197a65a00d7d1  gnutls-2.12.20.tar.bz2

contrib/src/gnutls/gnutls-win32.patch

---- gnutls-2.2.5/gl/gai_strerror.c	2008-02-21 08:58:18.000000000 +0100
-+++ gnutls/gl/gai_strerror.c	2008-05-22 08:20:56.000000000 +0200
-@@ -62,7 +62,7 @@
+--- gnutls-2.12.20/gl/gai_strerror.c.orig	2012-03-01 16:45:12.000000000 +0100
++++ gnutls-2.12.20/gl/gai_strerror.c	2012-09-27 14:39:30.273584236 +0200
+@@ -75,7 +75,7 @@
      { EAI_IDN_ENCODE, N_("Parameter string not correctly encoded") }
  #endif
    };
@@ -9,23 +9,20 @@
  const char *
  gai_strerror (int code)
  {
-@@ -73,6 +73,7 @@
- 
-   return _("Unknown error");
- }
-+#endif
- #ifdef _LIBC
+@@ -89,4 +89,5 @@
+ # ifdef _LIBC
  libc_hidden_def (gai_strerror)
- #endif
-
---- gnutls/lib/gnutls.pc.in.orig	2011-11-26 14:40:52.343740836 -0500
-+++ gnutls/lib/gnutls.pc.in	2011-11-26 14:41:49.456024042 -0500
+ # endif
++#endif
+ #endif /* !HAVE_DECL_GAI_STRERROR */
+--- gnutls-2.12.20/lib/gnutls.pc.in.orig	2012-09-27 14:40:07.243581693 +0200
++++ gnutls-2.12.20/lib/gnutls.pc.in	2012-01-06 20:06:23.000000000 +0100
 @@ -19,7 +19,7 @@
  Description: Transport Security Layer implementation for the GNU system
  URL: http://www.gnu.org/software/gnutls/
  Version: @VERSION@
 -Libs: -L${libdir} -lgnutls
 +Libs: -L${libdir} -lgnutls -lws2_32 -lcrypt32 @LTLIBINTL@
- Libs.private: @LTLIBGCRYPT@ @NETTLE_LIBS@
+ Libs.private: @LTLIBGCRYPT@ @LTLIBNETTLE@ @NETTLE_LIBS@ @GNUTLS_ZLIB_LIBS_PRIVATE@
  @GNUTLS_REQUIRES_PRIVATE@
  Cflags: -I${includedir}

contrib/src/gnutls/rules.mak

 # GnuTLS
 
-GNUTLS_VERSION := 2.12.7
+GNUTLS_VERSION := 2.12.20
 GNUTLS_URL := http://ftp.gnu.org/pub/gnu/gnutls/gnutls-$(GNUTLS_VERSION).tar.bz2
 
 PKGS += gnutls
@@ -28,6 +28,7 @@ endif
 
 GNUTLS_CONF := \
 	--disable-gtk-doc \
+	--without-p11-kit \
 	--disable-cxx \
 	--disable-srp-authentication \
 	--disable-psk-authentication-FIXME \