Add (void) to some macros to satisfy compiler.

More modern versions of GCC (at least with aarch64) are warning about an
unused value in these locations. It's incorrect, but I guess that the
macro is confusing it.

Using a (void) tag is a little ugly but solves the problem.

Change-Id: If6ba5083ab6e501c81e7743ae1ed99a89565e57c
Reviewed-on: https://boringssl-review.googlesource.com/2810
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/ssl_cert.c b/ssl/ssl_cert.c
index ed8b524..624c41a 100644
--- a/ssl/ssl_cert.c
+++ b/ssl/ssl_cert.c
@@ -801,7 +801,7 @@
     X509_free(x);
   }
 
-  sk_X509_NAME_set_cmp_func(stack, oldcmp);
+  (void) sk_X509_NAME_set_cmp_func(stack, oldcmp);
 
   return ret;
 }
diff --git a/ssl/ssl_ciph.c b/ssl/ssl_ciph.c
index ed4e81b..fb8c047 100644
--- a/ssl/ssl_ciph.c
+++ b/ssl/ssl_ciph.c
@@ -1127,7 +1127,7 @@
     }
     *cipher_list_by_id = tmp_cipher_list;
     tmp_cipher_list = NULL;
-    sk_SSL_CIPHER_set_cmp_func(*cipher_list_by_id, ssl_cipher_ptr_id_cmp);
+    (void) sk_SSL_CIPHER_set_cmp_func(*cipher_list_by_id, ssl_cipher_ptr_id_cmp);
 
     sk_SSL_CIPHER_sort(*cipher_list_by_id);
   } else {
diff --git a/ssl/ssl_sess.c b/ssl/ssl_sess.c
index 117e53c..367b0f4 100644
--- a/ssl/ssl_sess.c
+++ b/ssl/ssl_sess.c
@@ -764,7 +764,7 @@
     /* timeout */
     /* The reason we don't call SSL_CTX_remove_session() is to
      * save on locking overhead */
-    lh_SSL_SESSION_delete(param->cache, sess);
+    (void) lh_SSL_SESSION_delete(param->cache, sess);
     SSL_SESSION_list_remove(param->ctx, sess);
     sess->not_resumable = 1;
     if (param->ctx->remove_session_cb != NULL) {