swrast: Support sampler object for texture fetching state

swrast: Support sampler object for texture fetching state

swrast needs to pass sampler object into all texture fetching functions
to use correct sampling state when sampler object is bound to the unit.
The changes were made using half manual regular expression replace.

v2: Fix NULL deref in _swrast_choose_triangle(), because the _Current
    values aren't set yet, so we need to look at our texObj2D. (anholt)

Signed-off-by: Pauli Nieminen <pauli.nieminen@linux.intel.com>
Reviewed-by: Brian Paul <brianp@vmware.com>