i965: fix 1D texture borders with GL_CLAMP_TO_BORDER

With 1D textures, GL_TEXTURE_WRAP_T should be ignored (only
GL_TEXTURE_WRAP_S should be respected).  But the i965 hardware
seems to follow the value of GL_TEXTURE_WRAP_T even when sampling
1D textures.

This fix forces GL_TEXTURE_WRAP_T to be GL_REPEAT whenever 1D
textures are used; this allows the texture to be sampled
correctly, avoiding "imaginary" border elements in the T direction.

This bug was demonstrated in the Piglit tex1d-2dborder test.
With this fix, that test passes.

src/mesa/drivers/dri/i965/brw_wm_sampler_state.c

@@ -178,6 +178,16 @@ static void brw_update_sampler_state(struct wm_sampler_entry *key,
       sampler->ss1.s_wrap_mode = BRW_TEXCOORDMODE_CUBE;
       sampler->ss1.t_wrap_mode = BRW_TEXCOORDMODE_CUBE;
    }
+   else if (key->tex_target == GL_TEXTURE_1D) {
+      /* There's a bug in 1D texture sampling - it actually pays
+       * attention to the wrap_t value, though it should not.
+       * Override the wrap_t value here to GL_REPEAT to keep
+       * any nonexistent border pixels from floating in.
+       */
+      sampler->ss1.r_wrap_mode = translate_wrap_mode(key->wrap_r);
+      sampler->ss1.s_wrap_mode = translate_wrap_mode(key->wrap_s);
+      sampler->ss1.t_wrap_mode = BRW_TEXCOORDMODE_WRAP;
+   }
    else {
       sampler->ss1.r_wrap_mode = translate_wrap_mode(key->wrap_r);
       sampler->ss1.s_wrap_mode = translate_wrap_mode(key->wrap_s);