Currently this is disabled by default
Use --validate command-line argument to enable
The following new features were added in the schema format:
* Union, intersection, and list types
* Keys can specify a union of known types on-the-fly
* Key and tag names can include wildcards (* and ?, glob-style)
* Tags support any_key=yes, which means unrecognized subtags will be ignored
* Tags and keys support deprecated=yes (unimplemented)
* Specify max=infinite instead of max=-1
