Work on negotiation

Add helpers to convert between pinos and gstreamer formats.
Use pinos formats in the API.
Work on removing some hardcoded stuff and instead use the real format
from the pinos server.
Use memfd and sealing.

spa/lib/format.c

@@ -0,0 +1,40 @@
+/* Simple Plugin API
+ * Copyright (C) 2016 Wim Taymans <wim.taymans@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <spa/format.h>
+
+SpaResult
+spa_format_to_string (const SpaFormat *format, char **result)
+{
+  SpaResult res;
+
+  if (format == NULL || result == NULL)
+    return SPA_RESULT_INVALID_ARGUMENTS;
+
+
+
+
+
+  return SPA_RESULT_OK;
+}