softpipe: disable vertex texturing with draw/llvm

This is a temporary work around to prevent crashes with glean/glsl1
(for example) which try to do vertex shader texturing.

src/gallium/drivers/softpipe/sp_screen.c

@@ -64,7 +64,12 @@ softpipe_get_param(struct pipe_screen *screen, enum pipe_cap param)
    case PIPE_CAP_MAX_TEXTURE_IMAGE_UNITS:
       return PIPE_MAX_SAMPLERS;
    case PIPE_CAP_MAX_VERTEX_TEXTURE_UNITS:
+#ifdef HAVE_LLVM
+      /* Softpipe doesn't yet know how to tell draw/llvm about textures */
+      return 0;
+#else
       return PIPE_MAX_VERTEX_SAMPLERS;
+#endif
    case PIPE_CAP_MAX_COMBINED_SAMPLERS:
       return PIPE_MAX_SAMPLERS + PIPE_MAX_VERTEX_SAMPLERS;
    case PIPE_CAP_NPOT_TEXTURES: