Add a mode argument to weston_buffer_reference which indicates whether a
buffer's storage may/will be accessed, or whether the underlying storage
will no longer be accessed, e.g. because it has been copied. This will
be used to retain a pointer to the weston_buffer whilst being able to
send a release event to the client.
Signed-off-by: Daniel Stone <daniels@collabora.com>
fdc7b9c352