python: Allow writing to buffers.

src/gallium/state_trackers/python/st_device.h

@@ -38,6 +38,13 @@ struct pipe_context;
 struct st_winsys; 
 
 
+struct st_buffer {
+   struct st_device *st_dev;
+   
+   struct pipe_buffer *buffer;
+};
+
+
 struct st_context {
    struct st_device *st_dev;
    
@@ -65,6 +72,13 @@ struct st_device {
 };
 
 
+struct st_buffer *
+st_buffer_create(struct st_device *st_dev,
+                 unsigned alignment, unsigned usage, unsigned size);
+
+void
+st_buffer_destroy(struct st_buffer *st_buf);
+
 struct st_context *
 st_context_create(struct st_device *st_dev);