Do something about SecurityRulesAttribute

[gluck]

After hours of debugging, found out the reason ILRepack roundtrip of NHibernate fails (or rather causes PEVerify errors) is caused by SecurityRules attribute being removed.

NHibernate specifies SecurityRules(Set.Level1) (aka "I'm a legacy assembly, don't verify me IL"), because it merges a .Net2 assembly and has to.

ILRepack should do something about that, ideally migrate the code to L2 SecurityRules but that's probably too complex.

References:
https://groups.google.com/forum/#!topic/nhibernate-development/qH-IWEByM3c
https://msdn.microsoft.com/en-us/library/bb397858(v=vs.110).aspx