Fix handling of fat pointer function arguments
Fix handling of fat pointer function arguments

The store for the "extra" data went to the wrong destination.

GBGamer/rust,aidancully/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,GBGamer/rust,graydon/rust,aidancully/rust,graydon/rust,GBGamer/rust,GBGamer/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,GBGamer/rust,aidancully/rust,GBGamer/rust