Only use Libgcrypt for GnuTLS < 2.12

Only initialize Libgcrypt threading functions on GnuTLS < 2.12 which
does not do this automatically. Also drop explicit linking against
Libgcrypt on newer GnuTLS version.

This should allow GKrellM to work with a GnuTLS that uses Nettle instead
of Libgcrypt as its cryptographic backend.

Changelog

@@ -16,6 +16,9 @@ GKrellM Changelog
 	* Bugfixes
 	  o Store lockfiles under /var/lock/gkrellm-UID directories to make
 	    lockfiles work for multiple users.
+	* Only link against and initialize Libgcrypt when building with
+	  GnuTLS < 2.12. This allows using GKrellM with GnuTLS versions built
+	  against Nettle instead of Libgcrypt.
 
 2.3.5 - Thu Oct 7, 2010
 ------------------------

src/configure

@@ -96,7 +96,12 @@ echo -n "Checking for gnutls... "
 echo "Checking for gnutls... " 1>& 5
 
 GNUTLS_INCLUDE="$(pkg-config gnutls --cflags 2>& 5 || true)"
-GNUTLS_LIBS="$(pkg-config gnutls --libs 2>& 5 || true) -lgnutls-openssl -lgcrypt"
+GNUTLS_LIBS="$(pkg-config gnutls --libs 2>& 5 || true) -lgnutls-openssl"
+
+# GnuTLS >= 2.12 does not need explicit gcrypt linking anymore
+if $(pkg-config --max-version=2.11.99 gnutls 2>& 5 || false); then
+	GNUTLS_LIBS="$GNUTLS_LIBS -lgcrypt"
+fi
 
 cat << EOF > test.c
 #include <gnutls/openssl.h>

src/mail.c

@@ -51,6 +51,9 @@
 #define MD5Update	MD5_Update
 #define MD5Final	MD5_Final
 
+#if GNUTLS_VERSION_NUMBER <= 0x020b00
+/* gcrypt mutex setup is only needed for GnuTLS < 2.12 */
+
 static int gk_gcry_glib_mutex_init (void **priv) {
     GMutex *lock = g_mutex_new();
     if (!lock)
@@ -90,6 +93,8 @@ static struct gcry_thread_cbs gk_gcry_threads_glib = {
   NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL
 };
 
+#endif
+
 #else
 
 #if defined(HAVE_SSL)
@@ -4340,7 +4345,10 @@ gkrellm_init_mail_monitor(void)
 	_GK.decal_mail_delay = 1;
 
 #ifdef HAVE_GNUTLS
+#if GNUTLS_VERSION_NUMBER <= 0x020b00
+	/* gcrypt mutex setup, only needed for GnuTLS < 2.12 */
 	gcry_control (GCRYCTL_SET_THREAD_CBS, &gk_gcry_threads_glib);
+#endif
 	gnutls_global_init();
 	SSL_load_error_strings();
 	SSL_library_init();