VDPAU surfaces cannot be shared across multiple device instances.
Thus the same instance must be used within a pipeline.

Sharing instances also saves resources (X11 server connections).

This provides a more traditional set of library function calls than the
VDPAU specification defines. Furthermore, this has libvdpau.so as a
conditional run-time linking dependency.

Note that this requires libvdpau 0.6 or later (0.4.1-8 on Debian) at
run-time due to a bug in libvdpau versions 0.4 through 0.5.

This uncomments the configure checks for HAVE_VDPAU. That way VDPAU can
be used even if libavcodec is missing or old.

This way, common.am can be included also in directories without a
Modules.am file.

These functions assume that sockets are file descriptors, never worked
properly on Windows. See also 3841c085.

This reverts commit db8ff4e3.

refs b2cce4d8

Signed-off-by: Rafaël Carré <funman@videolan.org>

avcodec_flush_buffers() may get or release frame buffers.
See also EndVideoDec().

With the previous commit, the vout wrapper's display pool is no longer
used ever if direct rendering is not in use. Removing it saves one
picture buffer.
Signed-off-by: Rafaël Carré <funman@videolan.org>