targets/xvmc-nouveau: convert to static/shared pipe-drivers

targets/xvmc-nouveau: convert to static/shared pipe-drivers

Similar to vdpau targets, we're going to convert the individual
target libraries into a single one.

The library can be built with the relevant pipe-drivers
statically linked in, or loaded as shared modules.
Currently we default to static.

Cc: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Tested-by: Thomas Helland <thomashelland90 at gmail.com>