changes to BLI_buffer

- assert if BLI_buffer_at() is called with an out of bounds value.
- add BLI_buffer_resize_data() macro which resizes and returns a pointer to the new array.
- warn if missing call to BLI_buffer_free().

source/blender/blenlib/intern/buffer.c

@@ -70,7 +70,8 @@ void BLI_buffer_resize(BLI_Buffer *buffer, int new_count)
 	buffer->count = new_count;
 }
 
-void BLI_buffer_free(BLI_Buffer *buffer)
+/* callers use BLI_buffer_free */
+void _bli_buffer_free(BLI_Buffer *buffer)
 {
 	if ((buffer->flag & BLI_BUFFER_USE_STATIC) == 0) {
 		if (buffer->data) {