llvmpipe: Define an winsys for LLVM. Drop pipe_winsys

lp_winsys will eventually be unified with softpipe's eventually, but we
are free to move quicker since we don't have the myriad of users yet.

Will provide a pipe_winsys adaptor from Keith's softpipe-private-winsys
soon.
diff --git a/src/gallium/drivers/llvmpipe/SConscript b/src/gallium/drivers/llvmpipe/SConscript
index 26bf8b0..6bceb84 100644
--- a/src/gallium/drivers/llvmpipe/SConscript
+++ b/src/gallium/drivers/llvmpipe/SConscript
@@ -26,6 +26,7 @@
 		'lp_bld_swizzle.c',
 		'lp_bld_tgsi_soa.c',		
 		'lp_bld_type.c',
+		'lp_buffer.c',
 		'lp_clear.c',
 		'lp_context.c',
 		'lp_draw_arrays.c',