Bind *package* during load-time

[davazp]

There is a limitation now to use package during bootstrapping.

The in-package macro sets *package* both at compile-time and load-time. load and compile-time are supposed to bind *package* so a file cannot change the package for other files.

However, during bootstrapping files are not really loaded. So *package* is not bound.

This means that next files will see the package changed by the previous file.