st/mesa: restore some parameter checking buffer object functions

These functions may be called from the VBO code (not just user GL calls)
so do some parameter sanity checking.

src/mesa/state_tracker/st_cb_bufferobjects.c

@@ -98,6 +98,11 @@ st_bufferobj_subdata(GLcontext *ctx,
 {
    struct st_buffer_object *st_obj = st_buffer_object(obj);
 
+   /* we may be called from VBO code, so double-check params here */
+   ASSERT(offset >= 0);
+   ASSERT(size >= 0);
+   ASSERT(offset + size <= obj->Size);
+
    st_cond_flush_pipe_buffer_write(st_context(ctx), st_obj->buffer,
 				   offset, size, data);
 }
@@ -115,6 +120,11 @@ st_bufferobj_get_subdata(GLcontext *ctx,
 {
    struct st_buffer_object *st_obj = st_buffer_object(obj);
 
+   /* we may be called from VBO code, so double-check params here */
+   ASSERT(offset >= 0);
+   ASSERT(size >= 0);
+   ASSERT(offset + size <= obj->Size);
+
    st_cond_flush_pipe_buffer_read(st_context(ctx), st_obj->buffer,
 				  offset, size, data);
 }