ignore has become a reserved word

[avl]

It seems the standard Rust test framework now uses the identifier 'ignore' as an attribute.

This means it isn't very wise of Savefile to also use this attribute-name.

All savefile attributes should probably be renamed to contain 'savefile_' as a prefix in their name.

This will be a very breaking change.

I expect to make this change for the 0.4-release.

[avl]

All attributes are now prefixed with 'savefile_'.