gallium/noop: no operation gallium driver

gallium/noop: no operation gallium driver

This driver is a fake swdri driver that perform no operations
beside allocation gallium structure and buffer for upper layer
usage.

It's purpose is to help profiling core mesa/gallium without
having pipe driver overhead hidding hot spot of core code.

scons file are likely inadequate i am unfamiliar with this
build system.

To use it simply rename is to swrast_dri.so and properly set
LIBGL_DRIVERS_PATH env variable.

Signed-off-by: Jerome Glisse <jglisse@redhat.com>