gst_sample_set_buffer
gst_sample_set_caps
gst_sample_set_segment
gst_sample_set_info
gst_sample_is_writable
gst_sample_make_writable
This commit makes it possible to reuse a sample object and avoid
unnecessary memory allocations, for example in appsink.
In addition, writability is now required to set the buffer list.
https://bugzilla.gnome.org/show_bug.cgi?id=795144
We need different export decorators for the different libs.
For now no actual change though, just rename before the release,
and add prelude headers to define the new decorator to GST_EXPORT.
Add a new simple miniobject that is a combination of a GstBuffer, GstCaps,
GstSegment and other arbitrary info organized in a GstStructure. This object can
be used to exchange samples between an element and the application or for
storing album art in tags etc.
