Fixes for instance_change. 

The instance_change() function does not actually carry over the "visible" flag. This game demonstrates that:
https://drive.google.com/file/d/0B1P7NepPcOslMmRCRFRFQjhiNFE/view?usp=sharing

Also, the variables that *do* carry over are set before the create() event is called (because it can override them). No test case for this, but it fixes a bug in An Untitled Story (and the alternative makes no sense).