gnutls-available-p can return duplicate capabilities; on my system, for
example, 'ClientHello Padding' appears twice.

Ok to commit?

* src/gnutls.c (Fgnutls_available_p): Avoid duplicating capabilities.

---
 src/gnutls.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/gnutls.c b/src/gnutls.c
index a0de0238c4..2840c2abe9 100644
--- a/src/gnutls.c
+++ b/src/gnutls.c
@@ -2801,22 +2801,24 @@ DEFUN ("gnutls-available-p", Fgnutls_available_p,
Sgnutls_available_p, 0, 0, 0,

   capabilities = Fcons (intern("macs"), capabilities);

+#  ifdef HAVE_GNUTLS_EXT__DUMBFW
+  capabilities = Fcons (intern("ClientHello Padding"), capabilities);
+#  endif
+
 #  ifdef HAVE_GNUTLS_EXT_GET_NAME
   for (unsigned int ext=0; ext < 100; ext++)
     {
       const char* name = gnutls_ext_get_name(ext);
       if (name != NULL)
         {
-          capabilities = Fcons (intern(name), capabilities);
+          Lisp_Object cap = intern (name);
+          if (NILP (Fmemq (cap, capabilities)))
+            capabilities = Fcons (cap, capabilities);
         }
     }
 #  endif
 # endif  /* HAVE_GNUTLS3 */

-#  ifdef HAVE_GNUTLS_EXT__DUMBFW
-  capabilities = Fcons (intern("ClientHello Padding"), capabilities);
-#  endif
-
 # ifdef WINDOWSNT
   Vlibrary_cache = Fcons (Fcons (Qgnutls, capabilities), Vlibrary_cache);
 # endif /* WINDOWSNT */
-- 
2.38.1.windows.1